Frame and data pattern structure for multi-carrier systems

ABSTRACT

The present invention relates to a transmitting apparatus ( 82 ) for transmitting signals in a multi carrier system on the basis of a frame structure, each frame comprising at least one signalling pattern and one or more data patterns, said transmitting apparatus ( 82 ) comprising frame forming means ( 59 ) adapted to arrange first signalling data in said at least one signalling pattern in a frame, and adapted to arrange data in said one or more data patterns in a frame, whereby the data of said one or more data patterns are arranged in data frames, each data frame comprising second signalling data and content data, transforming means ( 60 ) adapted to transform said at least one signalling pattern and said one or more data patterns from the frequency domain into the time domain in order to generate a time domain transmission signal, and transmitting means ( 61 ) adapted to transmit said time domain transmission signal. 
     The present invention further relates to a corresponding transmitting method and frame structure, as well as a receiving apparatus and method and a system and a method for transmitting and receiving signals.

The present invention is directed to a new frame and data patternstructure for multi-carrier systems.

The present invention is hereby mainly directed (but not limited) tobroadcast systems, such as for example cable based or terrestrialdigital broadcast systems, in which content data, signalling data, pilotsignals and so forth are mapped on to a plurality of frequency carriers,which are then transmitted in a given overall or complete transmissionbandwidth. The receiver typically tunes to a partial channel (part ofthe overall transmission bandwidth) out of the complete channelbandwidth (sometimes called segmented reception) in order to receiveonly the content data which are necessary or wanted by the respectivereceiver. For example, in the ISDB-T standard, the overall channelbandwidth is hereby divided into 13 fixed segments of an equal length(equal number of frequency carriers).

The object of the present invention is to provide a transmittingapparatus and method, as well as a signal structure for a multi-carriersystem, which allow a flexible tuning to any required part of thetransmission bandwidth and which has a low overhead.

The above object is achieved by a transmitting apparatus according toclaim 1. The transmitting apparatus of the present invention is adaptedto transmit signals in a multicarrier system on the basis of a framestructure, each frame comprising at least one signalling pattern and oneor more data patterns, said transmitting apparatus comprising frameforming means adapted to arrange first signalling data in said at leastone signalling pattern in a frame and adapted to arrange data in saidone or more data patterns in a frame, whereby the data of said one ormore data patterns are arranged in data frames, each data framecomprising second signalling data and content data, transforming meansadapted to transform said at least one signalling pattern and said oneor more data patterns from the frequency domain into the time domain inorder to generate a time domain transmission signal, and transmittingmeans adapted to transmit said time domain transmission signal.

The above object is further achieved by a transmitting method accordingto claim 7. The transmitting method according to the present inventionis adapted to transmit signals in a multicarrier system on the basis ofa frame structure, each frame comprising at least one signalling patternin one or more data patterns, and comprises the steps of arrangingsignalling data in said at least one signalling pattern in a frame,arranging data in said one or more data patterns in a frame, whereby thedata of said one or more data patterns are arranged in data frames, eachdata frame comprise second signalling data and content data,transforming said at least one signalling pattern and said one or moredata patterns from the frequency domain into the time domain in order togenerate a time domain transmission signal, and transmitting said timedomain transmission signal.

The above object is further achieved by a frame pattern for amulticarrier system according to claim 8, comprising at least onesignalling pattern and one or more data patterns, wherein data arearranged in said one or more data patterns in a frame, whereby the dataof said one or more data patterns are arranged in data frames, each dataframe comprising second signalling data and content data.

The object of the present invention is further to provide a receivingapparatus and method, as well as a transmitting and receiving system andmethod, which allow a flexible tuning to any required part of thetransmission bandwidth and which has a low overhead.

The above object is achieved by a receiving apparatus for receivingsignals in a multi carrier system on the basis of a frame structure in atransmission bandwidth, according to claim 9, each frame comprising atleast one signalling pattern comprising first signalling data and one ormore data patterns, whereby the data of said one or more data patternsare arranged in data frames, each data frame comprising secondsignalling data and content data, said receiving apparatus comprisingreceiving means adapted to be tuned to and to receive a selected part ofsaid transmission bandwidth, said selected part of said transmissionbandwidth covering at least one data pattern to be received, evaluationmeans adapted to evaluate said second signalling data comprised in areceived data frame, and data de-mapping means adapted to de-map datafrom frequency carriers of a received data frame on the basis of theresult of said evaluation.

The above object is further achieved by a receiving method for receivingsignals in a multi carrier system on the basis of a frame structure in atransmission bandwidth, according to claim 14, each frame comprising atleast one signalling pattern comprising first signalling data and one ormore data patterns, whereby the data of said one or more data patternsare arranged in data frames, each data frame comprising secondsignalling data and content data, comprising the steps of receiving aselected part of said transmission bandwidth, said selected part of saidtransmission bandwidth covering at least one data pattern to bereceived, evaluating said second signalling data comprised in a receiveddata frame, and de-mapping data from frequency carriers of a receiveddata frame on the basis of the result of said evaluation.

The above object is further achieved by a system for transmitting andreceiving signals, according to claim 15, comprising a transmittingapparatus for transmitting signals in a multi carrier system on thebasis of a frame structure, each frame comprising at least onesignalling pattern and one or more data patterns, said transmittingapparatus comprising frame forming means adapted to arrange firstsignalling data in said at least one signalling pattern in a frame, andadapted to arrange data in said one or more data patterns in a frame,whereby the data of said one or more data patterns are arranged in dataframes, each data frame comprising second signalling data and contentdata, transforming means adapted to transform said at least onesignalling pattern and said one or more data patterns from the frequencydomain into the time domain in order to generate a time domaintransmission signal, and transmitting means adapted to transmit saidtime domain transmission signal, said system further comprising areceiving apparatus according to present invention adapted to receivesaid time domain transmission signal from said transmitting apparatus.

The above object is further achieved by a method for transmitting andreceiving signals, according to claim 16, comprising a transmittingmethod for transmitting signals in a multi carrier system on the basisof a frame structure, each frame comprising at least one signallingpattern and one or more data patterns, comprising the steps of arrangingsignalling data in said at least one signalling pattern in a frame,arranging data in said one or more data patterns in a frame, whereby thedata of said one or more data patterns are arranged in data frames, eachdata frame comprising second signalling data and content data,transforming said at least one signalling pattern and said one or moredata patterns from the frequency domain into the time domain in order togenerate a time domain transmission signal, and transmitting said timedomain transmission signal, said method further comprising a receivingmethod according to the present invention adapted to receive said timedomain transmission signal.

Advantageous features are defined in the dependent claims.

The present invention therefore suggests a multi-carrier system whichuses a frame structure or frame pattern in the frequency domain. In thefrequency domain, each frame comprises at least one signalling pattern,which carries first signalling data on frequency carriers. The at leastone signalling pattern may have additional pilot signals on frequencycarriers. Alternatively, each frame could have a dedicated trainingsequence or pattern which is arranged before (in time) the at least onesignalling pattern, whereby the training sequence or pattern carriesexclusively pilot signals. In this case, the at least one signallingpattern does not need (but can have) pilot signals. Further, each framecomprises one or more data patterns which follow the at least onesignalling pattern in time in each frame pattern. Further, according tothe present invention, each of the one or more data patterns of a framein a frequency domain may comprise at least one pilot signal arrangedamong said data of the data pattern. The at least one pilot signal ineach data pattern enables the receiving side to perform a channelestimation for the frequency carriers carrying the data in the datapatterns, in a simple way since the location of the pilot signal in thetime/frequency grid of the frequency domain is known to the receiver.

The present invention suggests to arrange the data in the one or moredata patterns in data frames, wherein each data frame comprises contentdata and second signalling data. Thus, the present invention suggests tosplit the arrangement and thus the transmission and reception of thesignalling data into the first signalling data which are transmitted inthe at least one signalling pattern in a frame, and the secondsignalling data which are arranged in the data frames. Hereby, it ispossible to transmit respectively identical first signalling data ineach of the at least one signalling patterns. In other words, if severalsignalling patterns are provided in a frame, each of the signallingpatterns may carry the identical first signalling data. These signallingdata are then signalling data which are valid for the entire frame. Thesecond signalling data, on the other hand, contain signalling data whichare only valid for the respective data frame. Thus, modulation, codingas well as other parameters of a data frame could be individuallysignalled with the second signalling data. The present inventiontherefore suggests a system which is very flexible but still effectivein view of the signalling overhead.

During the conversion from the frequency into the time domain, themapping of the first signalling data (as well as eventually the pilotsignals) of the one or more signalling patterns as well as the mappingof the content data and second pilot signals (as well as eventually thepilot signals) of the data patterns onto the frequency carriers takesplace. This conversion is e.g. implemented in an Inverse Fouriertransformation means or any other suitable transformation means. In theresulting time domain signal, each frame then comprises a respectivesignalling symbol (eventually preceded by a training symbol) as well asone or more data symbols. Each frame pattern covers the entire oroverall transmission band in the frequency direction. The receivingapparatus can be freely, flexibly and quickly tuned to any wanted partof the transmission bandwidth, provided that the part of thetransmission bandwidth to which the receiving apparatus can be tuned hasat least the length of one of the signalling patterns. Hereby, thereceiving apparatus is always able to receive the first signalling dataof an entire signalling pattern, so that on the basis and using thefirst signalling data comprising the physical layer informationnecessary for the receipt of the succeeding data patterns, the datapatterns can be received in the receiving apparatus. In case that eachsignalling pattern not only comprises first signalling data, but alsopilot signals, it is not necessary to provide dedicated preambles ortraining patterns consisting only of pilot signals, since the pilotsignals comprised in the signalling pattern allow the necessaryfrequency offset detection and compensation in the receiving apparatus,so that the overall overhead is reduced. However, it is also possible toprovide dedicated preambles for training patterns with pilot signalswhich precede the signalling patterns, which in this case do notcomprise pilot signals. The present invention is particularlyadvantageous in systems having a rather high signal-to-noise ratio, suchas but not limited to cable based systems. Although the receiver can beflexibly tuned to any wanted part of the transmission bandwidth, it isalways possible to receive the first signalling data and the other data(content data) due to the new frame structures suggested by the presentinvention. Further, the new frame structure enables a fast tuning of thereceiving apparatus to the wanted part of the transmission bandwidth.Since the content data are transmitted in data frames, wherein each dataframe comprises content data as well as second signalling data, thereceiving apparatus is able to receive the content data in a veryflexible manner, since the second signalling data comprised in each dataframe enable an individual signalling of the parameters of each dataframe.

Advantageously, the second signalling data comprise the modulation ofthe data in the received data frame, whereby the evaluation means of thereceiving apparatus is adapted to obtain the modulation and said datade-mapping means is adapted to perform a demodulation of the contentdata from frequency carriers of the received data frame on the basis ofthe obtained modulation. Further advantageously, the second signallingdata comprise the error coding of the content data in the received dataframe, whereby the evaluation means of the receiving apparatus isadapted to obtain the error coding and forward the error coding to anerror decoding means adapted to perform an error decoding on the contentdata of the received data frame.

Further advantageously, the second signalling data comprise connectionidentification and said evaluation means of the receiving apparatus isadapted to obtain said connection identification. The connectionidentification is for example information about broadcast, unicast,point-to-point communication and the like and enables the receivingapparatus to identify if the content data in the data frame are intendedto be received by the receiving apparatus or not.

Further advantageously, the receiving apparatus comprises a correlationmeans adapted to perform a correlation on a synchronization sequencecomprised in the second signalling data of a received data frame,whereby the data de-mapping means of the receiving apparatus is adaptedto de-map said content data from frequency carriers of the received dataframe on the basis of the result of the correlation.

Advantageously, the second signalling data in each data frame arearranged in a header of the data frame. Further advantageously, thesecond signalling data comprise a synchronization sequence. Thesynchronization sequence could for example be a pseudo-noise sequence, aPRBS (pseudo random binary sequence) or any other suitable sequence.Hereby, advantageously, the second signalling data are arranged insymbols and a part of said synchronization sequence is inserted in eachsymbol. Hereby, the most significant bit of each symbol could comprisesaid part of said synchronization sequence. Also, other bits of eachsymbol could be used for the transmission of said part of saidsynchronization sequence. Alternatively, the second signalling data arearranged in symbols and a part of said synchronization sequence ismodulated onto at least a part of each symbol. For example, one bit ofeach symbol could have one part (e.g. one bit) of the synchronizationsequence modulated onto it.

Thus, using the synchronization sequence, which could for example be apseudo-noise sequence or any other suitable sequence enabling a correctcorrelation in the receiving apparatus, the receiving apparatus is ableto find the second signalling data within a data frame, to evaluate thecontent of the second signalling data and then to decode, demodulate andso forth the content data comprised in the respective data frame. Thisis particularly necessary in (further advantageous) cases in which theat least one of said data patterns in a frame is followed by at leastone additional data pattern in the time dimension having the samefrequency structure (location within a frame as well as number offrequency carriers) as at least one of said data patterns, wherein dataframes arranged in said at least one of said data patterns and the atleast one additional data pattern are arranged succeeding each otherindependent of the frequency structure. In other words, the data framesare arranged within the data patterns, but with a structure which is notlimited to and independent of the structure of the data patterns. Thus,in case of a frame which comprises a number of data patterns whichsucceed each other in the time dimension, having the same frequencystructure (in other words are aligned to each other), the data framescomprising the data content and the second signalling data are arrangedwithin these data patterns succeeding each other in a free and flexiblemanner. Hereby, the length of each data frame as well as the parametersof the data frame, such as error coding, modulation and so forth, can beflexibly set and used for each data frame, e.g. can be different foreach data frame or at least some data frames. The respective parameterinformation for each individual data frame is then contained in thesecond signalling data, so that the content data in the data frame canbe properly received, decoded, demodulated and so forth in the receivingapparatus. Further, the second signalling data could contain connectionidentification information, i.e. information enabling a receivingapparatus to identify if the transmitted content data in the respectivedata frame is meant to be received by the receiving apparatus. Thus,broadcast transmission, unicast transmission, point-to-pointtransmission and so forth is supported by the present invention. Usingthe synchronization sequence contained in the second signalling data ineach data frame, the receiving apparatus is able to find the secondsignalling data within a data frame, to evaluate the content of thesecond signalling data and then to decode, demodulate and so forth thecontent data comprised in the respective data frame. In order to avoidany errors and mistakes, it has to be ensured that the second signallingdata in each data frame are encoded with a robust error coding scheme aswell as a robust modulation.

Advantageously, the at least one data pattern depends on a minimum datapattern length (in the frequency direction), namely is equal to one or amultiple of a minimum data pattern length. Thus, in case that two ormore or a plurality of data patterns is provided in a frame, the datapatterns could have different lengths. However, the length of the datapatterns depends on the minimum data pattern length as stated.Therefore, although the length of the data patterns is or may bevariable, the overhead is reduced, i.e. the amount of first signallingdata which need to be transmitted from a transmitter side to a receivingside is reduced as compared to a system in which the data pattern lengthis completely variable and can be set to any desired value. Since eachdata pattern is equal to one or a multiple of the minimum data patternlength, the overall transmission bandwidth may be a multiple of theminimum data pattern length.

Advantageously each frame comprises at least one signalling patternhaving first signalling data arranged on frequency carriers, said firstsignalling data comprising the length of each of said one or more datapatterns in reference to (or in terms of) said minimum data patternlength, said receiving apparatus further comprising evaluation meansadapted to extract said length from received first signalling data.Further advantageously the number of pilot signals in each received datapattern is directly proportional to the number of minimum data patternslengths comprised in said received data pattern, wherein said channelestimation means of said receiving apparatus is adapted to perform achannel estimation on the basis of said pilot signals. Thus, since aspecific and fixed number of pilot signals is allocated to and comprisedin the minimum data pattern length, for example one pilot signal, twopilot signals, three pilot signals or suitable number of pilot signals,each data pattern has a resulting number of pilot signals mapped ontoits frequency carriers.

Further advantageously, the pilot signals are arranged in the one ormore data patterns with a pilot signal pattern, wherein said minimumdata pattern length depends on the density of said pilot signals in thepilot pattern. Hereby, the term pilot signal pattern is intended tocharacterize a certain structure and arrangement of pilot signals in thetime/frequency grid of a frame (in the frequency domain), whereby theentire pilot signal pattern or at least some parts of it comprise pilotsignals arranged in a regular pattern in the time and/or the frequencydirection. Advantageously, the minimum data pattern length depends onthe density of the pilot signals in the pilot pattern. Hereby, the lowerthe pilot signal density is, the larger the minimum data pattern lengthcan be and vice versa. Therefore, in a system, in which less pilotsignals (a lower density of pilot signals) are necessary in order toachieve a reliable channel estimation on the receiver side, the minimumdata pattern length can be larger as compared to systems in which ahigher pilot signal density is needed. Advantageously, the pilot signalsin the pilot signal pattern have a regular spacing in the frequencydirection, whereby the minimum data pattern length corresponds to thespacing between two adjacent pilot signals in a frequency direction.Hereby, it is ensured that each data pattern only comprises a singlepilot signal. Of course, it is also possible that the minimum datapattern length could be chosen so that two or more pilot signals arecomprised in each data pattern. Further advantageously, each datapattern has the same length in the time direction. While the datapattern length could (but not necessarily must be) variable in the timedirection, this advantageous option suggests to provide each datapattern with the same length in the time direction (also called timedomain). Hereby, the length of the data patterns in the time directionmay advantageously correspond to the spacing between two adjacent pilotsignals in the time direction.

Further advantageously a time de-interleaving means is provided in saidreceiving apparatus which is adapted to perform a block wise timede-interleaving on received data patterns with a block lengthcorresponding to a multiple of the data pattern length in the timedirection

As explained above, under one option of the present invention, the framestructure of the present invention may comprise signalling patternshaving pilot signals. Hereby, advantageously, the frame structurecomprises at least two signalling patterns adjacent to each other in thefrequency direction and at least one data pattern following thesignalling patterns in the time direction, whereby first signalling dataand pilots are arranged in said at least two signalling patterns in theframe, each signalling pattern having the same length. Advantageously,said pilot signals arranged in said at least two signalling patterns ina frame form a pilot signal sequence. In other words, all pilot signalsof a frame form a pilot signal sequence. Alternatively, said pilotsignals in each one of said at least two signalling patternsadvantageously form a pilot signal sequence, wherein the pilot signalsequences are different from each other. Advantageously, said pilotsignal sequence is a pseudo random binary sequence. Advantageously, saidframe forming means is adapted to arrange said pilot signals onfrequency carriers of said at least two signalling patterns with adifferential modulation scheme. Advantageously, a pilot signal is mappedonto every m-th frequency carrier of said at least two signallingpatterns, m being an integer >1. Advantageously, each of said at leasttwo signalling patterns comprises at least one pilot band and said pilotsignals are mapped onto frequency carriers of said at least one pilotband.

Further advantageously, as already mentioned, each frame comprises atleast one additional data pattern succeeding said one or more datapatterns in the time dimension (i.e. direction), each of said additionaldata patterns having the respective same length as the corresponding oneof said previous data patterns. In other words, the structure of thedata pattern(s) in each frame is advantageously set up in a way that theone or more data patterns are arranged in the frequency dimension sothat the entire transmission bandwidth is covered. At least oneadditional data pattern is then arranged in the same frame but followingthe at least one data pattern in the time direction, whereby eachadditional or following data pattern has the same length (in thefrequency dimension or direction) as the previous data pattern in thesame frequency position. Thus, if a receiving apparatus is tuned to aspecific part of the transmission bandwidth, several data patterns perframe can be received, whereby said several data patterns have the samelength (in the frequency dimension) and follow each other in the timedimension.

In the frequency dimension, the length of each of the data patternstransmitted by the transmitting apparatus could be fix (permanent) orcould be adjusted dynamically. Alternatively or additionally, the numberof additional data patterns in the time dimension could be adjusteddynamically. Also, the length of the data patterns in one frame in thetime direction, i.e. the length of the time slots could be fixed orcould be varying. Hereby it is important that the signalling patterns ofthe next frame all start at the same time point. Any dynamic changes inrespect to the data patterns will then be signalled in the signallingpatterns. The multi-carrier system with the frame structure as suggestedby the present invention thus enables a very flexible transmission ofdata content in which the length of data patterns, and thus the amountof data per data pattern can be dynamically changed, for example fromframe to frame or in any other required way. Alternatively, the lengthand/or the number of the data patterns may be fixed or permanent.

It has to be understood that the present invention can be applied to anykind of multi-carrier system in which a transmitting apparatus isadapted to transmit data in an entire transmission bandwidth and areceiving apparatus is adapted to selectively receive only a part ofsaid entire transmission bandwidth. Non limiting examples for suchsystems may be existing or future uni-directional or bi-directionalbroadcast systems, such as wired or wireless (for example cable based,terrestrial etc.) digital video broadcast systems. The non limitingexample for a multi-carrier system would be an orthogonal frequencydivision multiplex (OFDM) system, however, any other suitable systemcould be used in which data, pilot signals and the like are mapped on aplurality of frequency carriers. The frequency carriers may hereby beequidistant and respectively have the same length (bandwidth). However,the present invention may also be used in multi-carrier systems in whichthe frequency carriers are not equidistant and/or do not have therespectively same length. Further, it should be understood that thepresent invention is not limited to any kind of specific frequency rangeneither in the overall transmission bandwidth applied on thetransmitting side nor on the selected part of the transmission bandwidthto which the receiving side is tuned. However, in some applications itmight be advantageous to use a receiving bandwidth on the receivingside, i.e. a bandwidth for the part of the transmission bandwidth towhich the receiver can be tuned, which corresponds to the bandwidth ofreceiving devices of existing (digital video broadcast or other)systems. A non limiting example for a receiver bandwidth may be 8 MHz,i.e. the receiving side can be tuned to any wanted 8 MHz bandwidth fromthe overall transmission bandwidth. Hereby, the overall transmissionbandwidth could be a multiple of 8 MHz, for example 8 MHz, 16 MHz, 24MHz, 32 MHz, 64 MHz, 256 MHz etc, so that the segmentation of theoverall transmission bandwidth, i.e. length of each signalling patterncould be 8 MHz. However, other segmentations are possible, e.g. (but notlimited to) a length of each signalling pattern of 4 MHz or 6 MHz.

Generally, in case of the non limiting example of 8 MHz for the receiverbandwidth, the length of each of the signalling patterns used in theframe structure of the present invention could be 8 MHz, 6 MHz, 4 MHz(or less).

The present invention is explained in more detail in the followingdescription of preferred embodiments in relation to the encloseddrawings, in which

FIG. 1 shows a schematic diagram of an entire transmission bandwidthfrom which a selected part can be selectively and flexibly received by areceiver,

FIG. 2 shows an example for a segmentation of the overall transmissionbandwidth,

FIG. 3 shows a schematic time domain representation of a frame structureaccording to the present invention,

FIG. 4 shows a schematic example of a frame structure or patternaccording to the present invention,

FIG. 5 shows a part of the frame structure of FIG. 4 with an explanationof a reconstruction of a signalling pattern,

FIG. 6 shows a schematic example of a receiver filter characteristic,

FIG. 7 shows a further example of a frame structure of pattern accordingto the present invention,

FIG. 8 shows a part of a further example of a frame structure or patternaccording to the present invention,

FIG. 9 shows a first example of an allocation of pilot signals to asignalling pattern,

FIG. 10 shows a second example of an allocation of pilot signals to asignalling pattern,

FIG. 11 shows a further example of a reconstruction of a signallingpattern,

FIG. 12 shows an example of the adaptation to different channelbandwidths,

FIG. 13 schematically shows an example of a frame structure of thepresent invention in the time dimension,

FIG. 14 shows a schematic block diagram of an example of a transmittingapparatus according to the present invention,

FIG. 15 shows a schematic block diagram of an example of a receivingapparatus according to the present invention,

FIG. 16 shows a schematic representation of a part of a frame structureaccording to the present invention,

FIG. 17 shows a schematic representation of a data frame according tothe present invention,

FIG. 18 shows a schematic representation of several data patterns havingthe same frequency structure and being arranged immediately succeedingeach other in the time dimension,

FIG. 19 shows a schematic representation of a part of the transmittingapparatus shown in FIG. 14, in which the data frames according to thepresent invention are formed,

FIG. 20 shows a first implementation example of a part of thetransmitting apparatus according to the present invention in which theheaders of the data frames of the present invention are formed,

FIG. 21 shows a second implementation example to form headers of thedata frames of the present invention,

FIG. 22 shows an implementation example of a part of the receivingapparatus according to the present invention to detect a synchronizationpeak from the data frame headers, and

FIG. 23 shows an implementation example of a part of the receivingapparatus according to the present invention to obtain the secondsignalling data.

FIG. 1 shows a schematic representation of an entire transmissionbandwidth 1, in which a transmitting apparatus according to the presentinvention, as for example the transmitting apparatus 82 schematicallyshown in FIG. 14, transmits signals in a multi-carrier system in linewith the present invention. FIG. 1 further schematically shows a blockdiagram of a receiving apparatus 3 of the present invention, which isadapted to be tuned to and selectively receive a selected part 2 of thetransmission bandwidth 1. Hereby, the receiving apparatus 3 comprises atuner 4 which is adapted to be tuned to and selectively receive thewanted part 2 of the transmission bandwidth 1 as well as furtherprocessing means 5 which perform the further necessary processing of thereceived signals in line with the respective communication system, suchas a demodulation, channel decoding and the like. A more elaborateexample of a receiving apparatus according to the present invention isshown in the schematic block diagram of FIG. 15, which shows a receivingapparatus 83 comprising a receiving interface 64, which can for examplebe an antenna, an antenna pattern, a wired or cable-based receivinginterface or any other suitable interface adapted to receive signals inthe respective transmission system or communication system. Thereceiving interface 64 of the receiving apparatus 83 is connected to areceiving means 65 which comprises a tuning means, such as the tuningmeans 4 shown in FIG. 1 as well as further necessary processing elementsdepending on the respective transmission or communication system, suchas down conversion means adapted to down convert the received signal toan intermediate frequency or the base band.

As stated above, the present invention enables a flexible and changingreception of a wanted part 2 of the transmission bandwidth 1 in areceiver by providing a specific and new frame structure for amulti-carrier system. FIG. 2 shows a schematic representation of anoverall transmission bandwidth 1, within which a transmitting apparatus82 (FIG. 14) of the present invention is adapted to transmit datacontent, such as video data, audio data or any other kind of data, indifferent segments or parts 6, 7, 8, 9 and 10. For example, the parts 6,7, 8, 9 and 10 could be used by the transmitting apparatus 82 totransmit different kinds of data, data from different sources, dataintended for different recipients and so forth. The parts 6 and 9 havefor example a maximum bandwidth, i.e. the maximum bandwidth which can bereceived by a corresponding receiving apparatus 83. The parts 7, 8 and10 have smaller bandwidths. It is now suggested to apply a framestructure or pattern to the entire transmission bandwidth 1 whereby eachframe comprises at least two signalling patterns adjacent to each otherin the frequency direction and a number of data patterns. Eachsignalling pattern has the same length and comprises first signallingdata as well as pilot signal mapped onto its frequency carriers(frequency subcarriers in the case of an OFDM system). In other words,the overall transmission bandwidth 1 is divided into equal parts for thesignalling patterns, whereby the maximum bandwidth to which a receivercan be tuned, for example the bandwidth shown for parts 6 and 9 in FIG.2, has to be equal or larger than the length of each signalling pattern.The new frame structure may therefore only comprise signalling patternsand data patterns, but not any separate training patterns or otherpatterns in which pilot signals are comprised. In other words, thepresent invention suggests a new frame structure with a preamble whichonly consists of two or more signalling patterns, and with data patternsfollowing the preamble in the time direction. Alternatively, thesignalling patterns could not have pilot signals, but could be precededby training patterns with pilot signals.

It should be noted that the length of the various data parts in thetransmission bandwidth cannot exceed the length (number of frequencycarriers) of the maximum bandwidth to which a receiver can be tuned aswill be explained in more detail further below.

FIG. 3 shows a schematic representation of an example of a time domainstructure of frames 11, 12 according to the present invention. Eachframe 11, 12 comprises one or more signalling symbols 13, 13′ andseveral data symbols 14, 14′. Hereby, in the time domain, the signallingsymbols are preceding the data symbols. Each frame 11, 12 may have aplurality of data symbols, wherein systems are possible in which thenumber of data symbols in each frame 11, 12 varies. The pilots signalscomprised in the signalling symbols are used in a receiving apparatus 83to perform channel estimation and/or integer frequency offsetcalculation. The time synchronization can e.g. be done by performing aguard interval correlation (or any other suitable technique) on guardintervals of received signalling symbols and/or data symbols in the timedomain. The signalling symbols 13, 13′ further contain signallinginformation (first signalling data), for example all physical layerinformation that is needed by the receiving apparatus 83 to decode thereceived signals, such as but not limited to L1 signalling data. Thefirst signalling data may for example comprise the allocation of datacontent to the various data patterns, i.e. for example which services,data streams, modulation, error correction settings etc. are located onwhich frequency carriers, so that the receiving apparatus 83 can obtaininformation to which part of the entire transmission bandwidth it shallbe tuned. It is possible that all signalling patterns in a frame containthe identical first signalling data. However, each signalling patternsmay additionally contain signalling data indicating the offset ordistance of the respective signalling pattern from the beginning of aframe so that the receiving apparatus 83 may optimize the tuning to thewanted part of the transmission frequency in a way that the receipt ofthe signalling patterns and the data patterns is optimized. On the otherhand, the offset or distance of the respective signalling pattern fromthe beginning of a frame can also be encoded in pilot signals, in pilotsignal sequences or in guard bands allocated to or comprised in thesignalling patterns, so that every signalling pattern in one frame canhave the identical signalling data. The use of the frame structureaccording to the present invention has the further advantage that bydividing the data stream into logical blocks, changes of the framestructure can be signalled from frame to frame, whereby a precedingframe signals the changed frame structure of the or one of thesucceeding frames. For example, the frame structure allows a seamlesschange of modulation parameters without creating errors.

FIG. 4 shows a schematic example of a frequency domain representation ofa frame structure or pattern 29 according to the present invention. Theframe structure 29 covers the entire transmission bandwidth 24 in thefrequency direction and comprises at least two signalling patterns 31adjacent to each other in the frequency direction, each carrying theidentical or almost identical first signalling data mapped on respectivefrequency carriers and having the same length. In the example shown inFIG. 4, the (first time slot of) entire transmission bandwidth 24 issub-divided into four signalling patterns 31, but any other higher orlower number of signalling patterns might be suitable. In thetransmitting apparatus 82 of the present invention as shown in FIG. 14,a frame forming means 59 is adapted to arrange the first signalling data(obtained from a modulating means 55) as well pilot signals (suppliedfrom a suitable source within the transmitting apparatus 82) in eachsignalling pattern. The signalling patterns are beforehand modulated bythe modulating means 55 with a suitable modulation scheme, e.g. a QAMmodulation or any other. Advantageously, a pseudo noise sequence or aCAZAC sequence is used for the pilot signals, but any other pilot signalsequence with good pseudo noise and/or correlation properties might besuitable. Each signalling pattern of a frame might comprise a differentpilot signal sequence, but alternatively, the pilot signals of thesignalling pattern of one frame might form a single pilot signalsequence.

It should be understood that the frame forming means 59 can beimplemented as a single module, unit or the like, or can be implementedas or in several modules, units, devices and so forth. Further, itshould be understood, that the frame forming means 59 may not form anentire frame structure or pattern 29 as shown in FIG. 4 (or framestructure or pattern 29′ as shown in FIG. 7) at one time point, but maybe adapted to form one part of the frame structure 29 (or 29′) afteranother in the time dimension (i.e. time slot after time slot). Forexample, the frame forming means 59 could be adapted to first arrangethe signalling patterns 31 as shown in FIG. 4 adjacent to each other aswell as to add the pilot signals as described above and below over theentire width of the transmission bandwidth 24 (i.e. in the example shownin FIG. 4, or for signalling patterns 31). Then, this part of the frame24 (the first time slot) could be further processed, for example bytransforming it from the frequency domain into the time domain, bybuilding a resulting time domain symbol (for example an OFDM symbol) andso forth. Then, in the next step, the frame forming means 59 could beadapted to process the line of data patterns 32, 33, 34, 35, 36, 37(i.e. the next time slot) in the manner which will be described furtherbelow over the entire transmission bandwidth 24, where after these datapatterns are further processed for example by transforming them from thefrequency domain into the time domain, by forming a time domain symbol(for example an OFDM symbol) and so forth. Thus, in the representationof FIG. 4, the frame structure 29 could be formed by the frame formingmeans 59 line wise or time slot wise, each part of the frame structure29 which extends over the entire transmission bandwidth 24 in thefrequency direction will be formed and processed as one block but theparts succeeding each other in the time direction (time slots) will beformed and processed one after the other.

The frame forming means 59 might be adapted to arrange said pilot signalso that a pilot signal will be mapped onto every m-th frequency carrier17 (m being a natural number larger than 1) in each signalling pattern,so that the frequency carriers 16 in between the pilots carry the firstsignalling data, as will be explained in more detail in relation to FIG.9 below. Additionally or alternatively, the frame forming means 59 maybe adapted to arrange pilot signals so that pilot signals will be mappedonto frequency carriers 20, 21 of at least one pilot band 18, 19comprised in a signalling pattern, as will be explained in more detailin relation to FIG. 10 below. A pilot band 18, 19 consists of a numberof immediately adjacent frequency carriers, onto which pilot signals aremapped. Hereby, each signalling pattern may have a single pilot band 18or may have two pilot bands 18, 19, one at the beginning and one at theend of the signalling pattern in the frequency direction. The length ofthe pilot bands (number of frequency carriers allocated to a pilot band)is advantageously the same for each signalling pattern. The length orbandwidth 39 of every signalling pattern 30 may be the same as thebandwidth 38 to which the tuner of the receiving apparatus 83 can betuned. However, the part of the transmission bandwidth to which thetuner of the receiving apparatus 83 can be tuned, may be larger than thelength of a signalling pattern 30. All the statements made above andbelow in relation to the pilot signals comprised in the signallingpatterns also apply to the pilot signals comprised in the data pattern,as explained below, e.g. in relation to FIG. 16.

The received pilots, i.e. pilot signals mapped on every m-th frequencycarrier and/or comprised in pilot bands of a received signallingpattern, (after transformation into the frequency domain in the time tofrequency transformation means 68, which is e.g. a Fouriertransformation means) are used for a channel estimation of the frequencycarriers in the frame in a channel estimation means 69, which provides ade-mapping means 70 with the necessary channel estimation informationenabling a correct de-mapping (i.e. demodulation) of the signalling datain the received signalling patterns. Also, the received pilots are usedin the receiving apparatus 83 for an integer frequency offset detectionin a corresponding integer frequency offset detection means 67 whichenables a detection and then a compensation of the integer frequencyoffset of the received signals. The integer frequency offset is thedeviation from the original (transmitted) frequency in multiples of thefrequency carrier spacing.

Each signalling pattern 31 may comprise the location of the signallingpattern 31 within the frame. For example each signalling pattern 31 ineach frame 29 has and carries the identical first signalling data andadditionally the location of the respective signalling pattern in theframe, which is different in each signalling pattern 31 in a frame. Thesignalling data are for example L1 signalling data which contain allphysical layer information that is needed by the receiving apparatus 83to decode received signals. However, any other suitable signalling datamay be comprised in the signalling patterns 31. The signalling patterns31 might for example comprise the location of the respective datasegments 32, 33, 34, 35, 36 so that a receiving apparatus 83 knows wherethe wanted data segments are located so that the tuner of the receivingapparatus 83 can tune to the respective location in order to receive thewanted data segments. Alternatively, as stated above, each signallingpattern of a frame might comprise the identical first signalling data,and the location of the respective signalling pattern within a frame issignalled (if at all) in a different way, e.g. by means of the pilotsignal sequence of the signalling patterns or by means of informationencoded in guard bands or the like. As stated above, each of thesignalling patterns 31 could comprise information about each of the datapatterns comprised in a frame. This information could include the datapattern length, the number and/or the location of the pilot signalscomprised in the data patterns. Hereby, the information on the length ofthe data patterns is e.g. expressed in terms of or referring to theminimum data pattern lengths. However, in order to reduce the overhead,each signalling pattern 31 could comprise information about only a partor some of the data patterns, for example but not limited to the oneswhich are located within (or located within and adjacent to) thefrequency band in which the signalling pattern 31 is located. In theexample of FIG. 4, the first signalling pattern 31 in the frame couldcomprise information about the data patterns 32 and 33 (and the timewise following data patterns 32′, 32″ . . . 33′, 33″ etc). The secondsignalling pattern in the frame could comprise information about thedata patterns 33, 34 and 35 (and the time wise following data patterns33′, 33″ . . . 34′, 34″ . . . 35′, 35″ etc).

In addition to the dedicated signalling patterns 31 as explained above,the frame structure also comprises additional second signalling dataembedded or comprised in the data patterns. According to the presentinvention, the content data in the data patterns are arranged in dataframes, wherein each data frame comprises a second signalling patternand content data. For example, each column of data patterns (i.e. datapatterns having the same frequency structure and succeeding each otherin the time direction), e.g. 33, 33′, 33″, 33′″, 33″″, could containdata frames with content data and second signalling data indicating themodulation used for content data in the respective data frame, theirerror coding and/or connection identification information enabling thereceiving apparatus to determine if the data is intended to be receivedor not. This reduces the implementation complexity in the receiver aswell as guarantees short delays for interactive services. Thispossibility applies to all embodiments of the present invention and willbe explained in more detail in relation to the FIGS. 17 to 20.

As shown in FIG. 15, the receiving apparatus 83, after the receivingmeans 65 with the tuner, comprises a time synchronization means 66adapted to perform time synchronization and a fractional frequencyoffset detection means 67 adapted to perform fractional frequency offsetdetection and compensation on the received time domain symbols. Thereceived time domain symbols are then supplied to a time to frequencytransformation means 68 for transforming the received time domainsignals into the frequency domain, where after the first signalling data(after an optional reconstruction in a reconstruction means 71), arede-modulated in a de-mapping means 72 and then evaluated in anevaluation means 73. The evaluation means 73 is adapted to extract thenecessary and required signalling information from the received firstsignalling data. If necessary, additional signalling patterns could beprovided in the time direction immediately succeeding the signallingpatterns 31.

The frame structure or pattern 29 further comprises at least one datapattern or segment extending over the entire or a part of the frequencybandwidth 24 in the frequency direction and following the signallingpatterns 31 in the time direction. In the time slot immediatelyfollowing the time slot in which the signalling patterns 31 are located,the frame structure 29 shown in FIG. 4 comprises several data segments32, 33, 34, 35, 36 and 37 with different lengths, i.e. a differentnumber of respective frequency carriers onto which data are mapped. Theframe structure 29 further comprises additional data segments insucceeding time slots, whereby the additional data patterns respectivelyhave the same length and number of frequency carriers as therespectively preceding data pattern. For example, the data pattern 32′,32″, 32′″ and 32′″ have the same length as the first data pattern 32.The data patterns 33′, 33″, 33′″ and 33″″ have the same length as thedata segment 33. In other words, the additional data patterns have thesame frequency dimension structure as the several data patterns 32, 33,34, 35, 36 and 37 in the first time slot after the signalling patterns31. Thus, if the receiving apparatus 83 for example tunes to a part 38of the transmission bandwidth in order to receive the data pattern 35,all time wise succeeding data patterns 35′, 35″ and 35″″ which have thesame length as the data pattern 35 can be properly received. Asmentioned above, the frame forming means 59 may form the respectivelines of data patterns extending over the entire transmission bandwidth24 one after the other (time slot by time slot). For example, the datapatterns 32, 33, 34, 35, 36, 37 will be formed by the frame formingmeans 59, and then transformed from the frequency domain into the timedomain. Afterwards, the data patterns 32′, 33′, 34′, 35′, 36′, 37′ willbe formed by the frame forming means 59 and then transformed from thefrequency domain into the time domain. Afterwards, the data patterns32″, 33″, 34″, 35″, 36″, 37″ will be formed by the frame forming means59 and then transformed from the frequency domain into the time domainand so forth. The transformation from the frequency to the time domainwill be done by a separate means, for example the frequency to timetransformation means 60 as described.

As mentioned earlier, the length of the one or more data patterns, e.g.the data patterns shown in the frame structures of FIG. 4 and FIG. 7,comprised in a frame structure according to the present invention eachcomprise at least one pilot signal, whereby the length of each of theone or more data patterns is equal to or a multiple of a minimum datapattern length. The minimum data pattern length can for example be setin a way that at least one pilot signal is comprised in each datapattern of a frame. Alternatively two, three, four, five or any othersuitable number of pilot signals could be comprised in one minimum datapattern length. Hereby, in some implementations it might be advantageousto choose rather small data pattern lengths in order to have a higherflexibility in the allocation of the data patterns for the transmissionof content data. Therefore, in some implementations it might be moreadvantageous to choose a minimum data pattern length so that only asingle one or may be two pilot signals are comprised in it. However,other implementations may be possible. Further, in some implementationsit might be useful to set the minimum data pattern length depending onthe density or number of pilot signals comprised in an entire frame. Forexample, in case that the pilot signals among the data patterns arechosen so that a good and reliable channel estimation on the receivingside is enabled without loosing too much transmission capacity (byallocating pilot signals to frequency carriers of data patterns insteadof data). For example, in systems in which the occurrence of multipatheffects or other negative effects necessitate the provision of a ratherhigh number (and resulting density) of pilot signals, the result willnormally be that the pilot signals are closer together (in frequencyand/or in time direction), so that the minimum data pattern length couldbe rather short if only a single pilot signal would be comprised in it.On the other hand, in case of systems in which a lower number (anddensity) of pilot signals is required in order to enable a reliablechannel estimation on a receiving side, the frequency and time directionspacing of the pilot signals could be comparatively large, so that theresulting minimum data pattern length could be longer. Normally, in thetime domain, guard intervals are provided in between data symbols or thedata symbols comprise guard intervals in order to cope with multipatheffects or other negative effects. Thus, there can be a correlationbetween the length of the guard intervals between the data symbols andthe density of the pilot signals in the data patterns of a frame. Thelonger the guard intervals are, the higher the number of the requiredpilot signals among the data patterns usually is and vice versa. Thus,the pilot signal density and number among the data patterns of a framecould be set depending on the guard interval length, so that the minimumdata pattern length could depend on the length of the guard intervals.

The provision of a minimum data pattern length which determines thelength of each of the data patterns within a frame reduces thesignalling overhead since the length of the data pattern has to becommunicated only by reference to the minimum data pattern length fromthe transmitter to the receiver. On the other hand, the location of thedata patterns within a frame is known to the receiver since entiretransmission bandwidth is a multiple of the minimum data pattern length.Thus, the frequency alignment, i.e. the frequency location in thetime/frequency grid in the frequency domain is always the same for thedata patterns and therefore known to the receiver, such as the receivingapparatus 83 as shown and explained in relation to FIG. 15. Further,particularly in case when the pilot signals form a pilot signal patternwith a regular spacing between adjacent pilot signals in the frequencyand the time direction, the location of the pilot signals in thetime/frequency grid is also known to the receiving apparatus so thatthey do not need to be signalled either. FIG. 16 shows an example of apilot signal pattern in a time/frequency grid. Specifically, FIG. 16shows a part of an entire frequency bandwidth, for example a data partof the frame shown in FIG. 4 or in FIG. 7 with a detailed representationof the frequency carriers in the frequency direction (horizontaldirection) and the time slots (vertical direction), each time slotresulting in a data symbol after frequency to time transformation. Inthe example shown in FIG. 16, the spacing of the pilot signals in thefrequency direction is 12, i.e. every 12^(th) frequency carrier carriesa pilot signal (all other frequency carriers carry data). However, ascan be seen in FIG. 16, “adjacent” pilot signals are not adjacent in thesame time slot, but in neighbouring or immediately adjacent time slots.This enables a better channel estimation in the receiving apparatus 83and the time direction. Alternatively, adjacent pilot signals in thefrequency direction could be allocated to the same time slot, or couldbe spaced by one, two or any other suitable number of time slots. In thetime direction, adjacent pilot signals are, for example shown in FIG.16, spaced by 4 time slots, i.e. every 4^(th) time slot carries a pilotsignal. Hereby, adjacent pilot signals in the shown example are locatedin the same frequency carrier. Alternatively, “adjacent” pilot signalsin the time direction could be located in immediately adjacent frequencycarrier, or spaced by 1, 2, 3 or any other suitable number of frequencycarriers. Thus case that the minimum data pattern length is set to thespacing between adjacent pilot signals in the frequency direction aswell as in the time direction, a single pilot signal would be comprisedwithin the minimum data pattern length, which has 12 frequency carriersin the frequency direction and 4 time slots in the time direction. Thus,the minimum data pattern comprises 48 pilot signals (which correspond toa pilot density of 1/48). In FIG. 16, two examples of possible datapatterns are indicated. The first data pattern has a lengthcorresponding to the minimum data pattern length, i.e. comprises 48frequency carriers, whereas the second data pattern comprises 3 minimumdata pattern lengths or sizes, i.e. comprises 144 frequency carriers.Generally, the use of such a pilot pattern having a regular distributionin the time and/or frequency direction or similar pilot pattern ensuresthat the pilot locations within the data patterns are easier to predictin the receiving apparatus 83.

The receiving apparatus 83 shown in FIG. 15 comprises the channelestimation means 69 which is adapted to perform a channel estimation onthe basis of the pilot signals received in data patterns and to providea de-mapping means 70 with the necessary channel estimation information.The de-mapping means 70 is thus able to de-map or de-modulate the datacorrectly from the (de-interleaved) frequency carriers on the basis ofthe channel estimation information.

Further, if every data pattern has the same length in the timedirection, this ensures a constant number of data symbols (in the timedomain) independent from the tuning position of the receiving apparatus83. In addition hereto, having the data pattern length being equal to ormultiple of a minimum data pattern length, an easier and betterpredictable adjustment of a time interleavers 63, 63′, 63″ of thetransmitting apparatus 82 and a time de-interleaver 77 comprised in thereceiving apparatus 63. The time interleavers 63, 63′, 63″ arerespectively arranged between data frame forming means 54, 54′, 54″ andthe frame forming means 59 and are adapted to perform time interleavingon the data. The time de-interleaver 77 of the receiving apparatus 83 islocated after the time to frequency transformation means 68 and beforethe de-mapping means 70 (as well as before the correlation means 78) andperforms time de-interleaving correspondingly. Specifically, the timeinterleavers 63, 63′, 63″ and the time de-interleaver 77 couldadvantageously be realized as block interleavers having a size whichdepends on the minimum data pattern length in the time direction.Advantageously, the block size is hereby a multiple of the minimum datapattern length, i.e. of the data patterns having the same length, in thetime direction (e.g. a multiple of 4 for the example of FIG. 16).

The flexible and variable data pattern structure of the frame structureor pattern 29 as suggested by the present invention can for example beimplemented in the transmitting apparatus 82 of the present invention asshown in FIG. 14 by mapping of various different data streams, forexample with different kinds of data and/or data from different sources,as visualized by the branches data 1, data 2 and data 3 in FIG. 14. Thecontent data of each branch are modulated according to the implementedmodulation scheme, e.g. QAM or any other suitable modulation, in arespective modulating means 58, 58′, 58″. Respective data frames withthe (modulated) content data and second signalling data are formed inrespective data frame forming means 54, 54′, 54″ which form the dataframes in the frequency dimension. The second signalling data arealready modulated with a suitable modulation, and before the respectivemodulation, the content data as well as the second signalling data werealready encoded by a suitable (error) coding scheme. The respectivecontent data and the second signalling data of the data frames as wellas the pilot signals (obtained from a suitable source within thetransmitting apparatus 82) are then arranged in the data patterns in theframe forming means 59, e.g. by a data pattern forming means comprisedin the frame forming means 59. The frame forming means 59 also forms thesignalling patterns with the first signalling data and the pilotsignals, e.g. by a signalling pattern forming means comprised in theframe forming means 59. The frame forming means 59 then forms the frameshaving the frame structures 29, 29′ with the signalling patterns and thedata patterns as described. As mentioned, the frame forming means 59could be implemented in one or several modules, or could also be part ofother processing units or modules. Further, the frame forming means 59may be adapted to form a frame 29 at succeeding time periods, forexample by first forming the sequence of signalling patterns 31extending over the entire transmission bandwidth 24, then by forming thesequence of data patterns 32, 33, 34, 35, 36, 37 extending over theentire transmission bandwidth 24 and so forth. The signalling data,content data as well as the respective pilot signals are then(separately and one after another) transformed from the frequency to thetime domain and mapped onto frequency carriers in the frequency to timetransforming means 60 (which is for example an Inverse Fast FourierTransformation means or the like). Hereby, it is to be noted that theframe structure 29, 29′ forms the basis for the frequency to timetransformation. The signalling data, content data as well as pilotsignals of each of the time slots (time units in the time dimension ofthe frame structures 29, 29′) of the entire transmission bandwidth 24are mapped onto the frequency carriers. In other words, all the patternsof the entire transmission bandwidth 24 in each time slot are alwaysmapped onto the necessary number of frequency carriers. For example thefirst time slot (i.e. all signalling patterns 31) of the frame structure29 of FIG. 4 would then result in a signalling symbol, the second timeslot (i.e. all data patterns 32, 33, 34, 35, 36, 37) of the framestructure would then result in a data symbol and so forth. Thecorrespondingly formed time domain symbols (e.g. OFDM symbols) are thensupplied from the frequency to time transforming means 60 to a guardinterval adding means 57 which adds guard intervals to the time domainsymbols. The thus formed transmission symbols are then transmitted by atransmitting means 61 via a transmitting interface 62

As stated, at least some of the various data patterns may have differentlengths, i.e. different numbers of frequency carriers in case that thefrequency carriers are equidistant and have the same bandwidth,respectively. Generally, the length of the data patterns in thefrequency direction needs to be smaller or at maximum equal to theeffective receiver bandwidth so that the data patterns can be receivedin the receiving apparatus 83. Further, the transmitting apparatus 82may be adapted to change the data pattern structure, e.g. the lengthand/or the number of the data patterns (in frequency and/or timedirection) dynamically. Alternatively, the structure of the datapatterns could be fixed or permanent.

Generally, the frame structure of the present invention could be fixedor permanent, i.e. the overall bandwidth as well as the extension ofeach frame in the time direction could be fixed and always the same.Alternatively, the frame structure can also be flexible, i.e. theoverall bandwidth and/or the extension of each frame in the timedirection could be flexible and changed from time to time depending onthe desired application. For example, the number of time slots with datapatterns could be flexibly changed. Hereby, the changes could besignalled to a receiving apparatus in the signalling data of thesignalling patterns.

During the start-up phase or initialization phase of the receivingapparatus 83, the receiving apparatus 83 tunes to an arbitrary frequencypart of the overall frequency bandwidth. In the non-limiting example ofa cable broadcast system, the signalling pattern 30 could for examplehave a 8 MHz bandwidth (it has to be understood, however, that thesignalling patterns could also have any other bandwidth, such as 4 MHz,6 MHz etc.). Thus, during the start-up phase, the receiving apparatus 83is able to receive an entire signalling pattern 30 in the original orre-ordered sequence and to perform a time synchronization in the timesynchronization means 66, e.g. by performing a guard intervalcorrelation on the guard intervals of received signalling symbols (ordata symbols) or by using any other suitable technique to obtain a timesynchronization. The receiving apparatus 83 further comprises thementioned fractional frequency offset detection means 67 adapted toperform a detection and calculation of the fractional frequency offsetof the received signals from fractions of the frequency carrier spacingin order to allow fractional frequency compensation. The thus obtainedfractional frequency offset information could then be supplied to thetuner comprised in the receiving means 65 which then performs fractionalfrequency compensation. The fractional frequency compensation could alsobe done by other suitable techniques. After transforming the receivedtime domain signals to the frequency domain in the time to frequencytransformation means 68 (which is for example a Fast FourierTransformation means or the like), the pilot signals in the receivedsignalling patterns are used to perform a channel estimation (usually acoarse channel estimation) in the channel estimation means 69 and/or aninteger frequency offset calculation. The integer frequency offsetcalculation is performed in an integer frequency offset detection means74 which is adapted to detect and calculate the frequency offset of thereceived signals from the original frequency structure, wherein thefrequency offset is counted in integer multiples of the frequencycarrier spacing (thus integer frequency offset). The thus obtainedinteger frequency offset information could then be supplied to the tunercomprised in the receiving means 65 which then performs integerfrequency compensation. The integer frequency compensation could also bedone by other suitable techniques. Since the fractional frequency offsethas already been calculated and compensated by means of the fractionalfrequency offset detection means 67, the complete frequency offsetcompensation can therefore be achieved. In the evaluation means 73 ofthe receiving apparatus 83, the received first signalling data areevaluated, for example the location of the received signalling patternin the frame is obtained so that the receiver can freely and flexiblytune to the respectively wanted frequency position, such as the part 38is shown in FIG. 4. However, in order to be able to properly evaluatethe first signalling data of the signalling patterns 31 in case that thetuning position of the receiving apparatus 83 does not match with thesignalling pattern structure, the received signalling signals have to bere-ordered which is performed in a re-constructing means 71 asdescribed. FIG. 5 shows this reordering in a schematic example. The lastpart 31′ of a previous signalling pattern is received before the firstpart 31″ of a succeeding signalling pattern, where after thereconstructions means 71 places the part 31′ after the part 31″ in orderto reconstruct the original sequence of the signalling data, where afterthe reordered signalling pattern is evaluated in the evaluation means 73after a corresponding de-mapping of the first signalling data from thefrequency carriers in the de-mapping means 72. It is to be rememberedthat the content of each signalling pattern 31 is the same, so that thisreordering is possible.

Often, a receiving apparatus does not provide a flat frequency responseover the complete receiving bandwidth to which the receiver is tuned. Inaddition, a transmission system usually faces increasing attenuation atthe boarder of the receiving bandwidth window. FIG. 6 shows a schematicrepresentation of a typical filter shape example. It can be seen thatthe filter is not rectangular, so that e.g. instead of 8 MHz bandwidth,the receiving apparatus is only able to effectively receive 7.61 MHzbandwidth. The consequence is that the receiving apparatus 83 may not beable to perform the reordering of the signalling data as described inrelation to FIG. 5 in case that the signalling patterns 31 have the samelength and bandwidth as the receiving bandwidth of the receivingapparatus 83, so that some signals are lost and cannot be received atthe border of the receiving bandwidth. In order to overcome thisproblem, and other problems and in order to ensure that the receivingapparatus 83 is always able to receive one complete signalling patternin the original sequence and does not have to reorder or rearrange thereceived signalling signals, the present invention alternatively oradditionally suggests to use signalling patterns 31 a which have areduced length as compared to the receiver bandwidth.

According to the example shown in FIG. 7, it is suggested to usesignalling patterns 31 a which have half the length of a receiverbandwidth, but still the same frequency structure. In other words,respective two (i.e. pairs) of the half length signalling patterns 31 aare matched and aligned with the receiver bandwidth. Hereby, each pairof signalling patterns 31 a would have the identical first signallingdata or almost identical first signalling data including the (varying)location of the signalling patterns 31 a in the respective frame.However, in relation to the other pairs of signalling patterns, in theseother pairs, since they have a respective different location within theframe, the signalling data would be identical except the locationinformation. In the above example of the receiving apparatus 83 having abandwidth or length of 8 MHz, the signalling pattern 31 a would theneach have a length or bandwidth of 4 MHz. Hereby, in order to ensurethat the same amount of first signalling data as before can betransmitted, it might be necessary to add additional half lengthsignalling patterns 31 b in the time slot succeeding the signallingpatterns 31 a and before the data patterns 32, 34, 35, 36 and 37. Theadditional signalling patterns 31 b have the same time and frequencyarrangement/alignment as the signalling patterns 31 a, but compriseadditional and different signalling information as the signallinginformation contained in the signalling patterns 31 a. In this way, thereceiving apparatus 83 will be able to receive the signalling patterns31 a and 31 b completely and the reconstruction means 71 of thereceiving apparatus is adapted to combine the first signalling data ofthe signalling patterns 31 a and 31 b to the original sequence. In thiscase, the reconstruction means 71 in the receiving apparatus 83 can beomitted.

It is also advantageously possible to only provide one time slot withhalf length signalling patterns 31 a if all necessary first signallingdata can be transmitted in the half length and the additional signallingpatterns 31 b are not necessary. In this case, each signalling pattern31 a comprises the identical (or almost identical) first signalling dataand each received signalling pattern 31 a enables the receivingapparatus 83 to always tune to and receive any wanted part of thetransmission bandwidth and thus the wanted data pattern(s).Alternatively, even more half length signalling patterns could be usedin the succeeding time slot after the signalling patterns 31 b.

It should be generally (for all embodiments of the present invention)noted that the length (or bandwidth) of the data patterns and/or thesignalling patterns could be adapted to, e.g. could be smaller than orat maximum equal to, the effective receiving bandwidth of the receivingapparatus 83, for example to the output bandwidth of the receiving bandpass filter, as described above.

Further, for all embodiments of the present invention, it could beadvantageous if one or more of the signalling patterns 31; 31 a, 31 bare succeeded in the time direction by one or more additional signallingpatterns with the same length and location within the frame. Forexample, the first signalling pattern in a frame could have one or moreadditional signalling patterns in the succeeding time slots. Theadditional signalling patterns could hereby have the identical or almostidentical signalling information as the first signalling pattern.Hereby, the other signalling patterns in a frame do not need to haveadditional signalling patterns. Generally, the number of signallingpatterns in each frequency location within a frame could be varying. Forexample, it could be advantageous if in each frequency location of aframe a number of signalling patterns is provided which is necessary inview of notches or other disturbances. Alternatively or additionally,the number of signalling patterns in each frequency location within aframe could be varying depending on the amount of signalling data.Hereby, for example, if more data patterns need to be signalized, moresignalling patterns could be necessary in the time direction. The lengthof the signalling patterns in the time direction could hereby be part ofthe first signalling data comprised in the signalling patterns.

In a non-limiting example, the transmission and reception of the firstsignalling data, e.g. L1 (Level 1) signalling data, and the additionalpilots, which are used for fractional frequency synchronization andchannel equalization, as well as the data patterns, is based on OFDM.The first signalling data are transmitted in blocks or patterns of e.g.4 MHz, but any other suitable size could be used. The only necessarycondition is to have one complete signalling pattern within the tuningwindow, but this condition could be fulfilled by using two or moresignalling patterns having a smaller size succeeding each other in thetime direction as described in relation to FIG. 7. Therefore, themaximum bandwidth of the signalling pattern may be e.g. the tuningwindow of a state-of-the-art tuner, i.e. 7.61 MHz.). Some numericalexamples are given in the following. In a first example, each signallingpattern 31; 31 a, 31 b covers exactly 4 MHz, while this corresponds to1792 OFDM frequency carriers while having duration T_(u) of the usefulpart of the OFDM symbol of 448 μs. In a second example, each signallingpattern covers 7.61 MHz (exactly 3409/448 usec), while this correspondsto 3409 OFDM carriers while having duration T_(U) of the useful part ofthe OFDM symbol of 448 μs.

According to a first aspect, a pilot signal is mapped to every m-thfrequency carrier 17 of a signalling pattern 31 a, as schematicallyshown in FIG. 9 (m is an integer >1). It has to be clear, however, thatthis possibility equally applies to the signalling pattern 31 shown inFIG. 4, or generally to signalling patterns of any suitable length. Thefrequency carriers 16 in between the pilot signal carrying frequencycarriers are carrying signalling data. The mapping of the firstsignalling data to the frequency carriers 16 and the mapping of thepilot signals 17 to every m-th frequency carrier is performed by thefrequency to time transformation means 60 and the arrangement of thepilots and the first signalling data in the signalling pattern isperformed by the frame forming means 59 comprised in the transmittingapparatus 82 as shown in FIG. 14. Generally, as stated above, the pilotsignals form a pilot signal sequence. Hereby, the pilots are for examplemodulated against each other by a differential modulation scheme, suchas but not limed to D-BPSK (differential binary phase shift keying). Themodulation is for example obtained by means of a PRBS (pseudo randombinary sequence register, e.g. 2̂23−1). The repetition rate of m shallallow unambiguous D-BPSK decoding on the receiving side, such as thereceiving apparatus 83 of the present invention as shown in FIG. 15,even for multi path channels. Repetition rates m are for example 7, 14,28, . . . for 4 MHz signalling patterns since 7, 14, 28 . . . aredividers of 1792 (==number of frequency carriers in a 4 MHz signallingpattern). In this example, an advantageous repetition value is m=7. Inother words, every 7-th frequency carrier carries a pilot signal evenacross adjacent signalling patterns. This example results in 256 pilotsignals per 4 MHz signalling pattern. However, other repetition valuesthan the above examples might be advantageous depending on therespective length of a signalling pattern and/or other factors.According to the invention, as described above, the data pattern(s) alsocarry pilot signals mapped on some of the frequency carriers in betweenthe frequency carriers with the data, whereby it can be advantageous ifthe pilot signals are mapped on frequency carriers of the datapattern(s) in location which correspond to the frequency carriers in thesignalling pattern(s) on which pilot signals are mapped. Generally, thedensity of the pilot signals in the data pattern(s) does not need to beas high as the density of the pilot signals in the signallingpattern(s). For example, if a pilot signal is mapped onto every m-thfrequency carrier in the signalling pattern(s) (m being an integer >1),a pilot signal could be mapped onto every n-th frequency carrier of thedata pattern(s), whereby n is an integer >1 and an integer multiple ofm. As an advantageous example, if m=7, then n=28 (or any other suitablenumber). The pilot signals in the data pattern(s) could also form apilot signal sequence as explained for the signalling pattern(s).

Regarding the creation of the pilot signal sequence for the signallingpattern(s) and the data pattern(s), which is for example a PN sequence,there are two options:

-   -   Option 1: Every signalling pattern in each frame carries a        different pilot signal sequence. In the above example, the        initialization of the PRBS register is aligned to the        transmission frequency. 256 pilots are located within every        frequency block of 4 MHz. The pilot signal sequence of each 4        MHz block is calculated separately. This allows a memory        efficient implementation on receiver side.    -   Option 2: The pilot signal sequence is applied once for all the        signalling patterns comprised in the complete transmission        bandwidth. The receiver, e.g. the receiving apparatus 83, stores        this known sequence, for example in a storage means, which can        be part of or may be external to the integer frequency offset        detection means 74, and extracts the frequency block that        corresponds to its current tuning position.

All other carriers 16 within the signalling pattern are used for thetransmission of the L1 signalling data. The start of the signalling datain each signalling pattern is always aligned to the 4 MHz structure,i.e. it always starts at multiples of 4 MHz in the depicted example.Each 4 MHz signalling pattern may carry exactly the same information,since the pilot signal sequences or the pilot signal sequence give thereceiving apparatus 83 information about the location of the respectivesignalling pattern in each frame. Alternatively, each signalling patternmay additionally comprise the location of the signalling pattern in theframe. Further, in order to reduce the peak-to-average power ratio ofthe output time domain signal, the signalling data of each signallingpattern may be scrambled in the transmitter by a unique scramblingsequence, which may be obtained by means of the signalling patternnumber.

In the receiving apparatus 83, the pilot signals comprised in thesignalling pattern 31; 31 a, 31 b are used (after a time to frequencytransformation of the received time domain symbols in the time tofrequency transformation means 68) in an integer frequency offsetdetection means 74 to detect the integer frequency offset, the result ofwhich is then used in the receiving apparatus 83 to perform integerfrequency offset compensation in the frequency domain. Morespecifically, the pilots signals (which are for example D-BPSKmodulated) comprised in the signalling patterns within the receivedfrequency range are demodulated in a demodulation means 75 comprised inthe integer frequency offset detection means 74. Then, a correlationmeans 76 comprised in the integer frequency offset detection means 74performs a correlation of the demodulated pilot signal (pilot signalsequences) with the stored or generated (expected) pilot signalsequence, e.g. a PRBS sequence, in order to get aligned in the exactfrequency offset. The correlation is done with the PRBS sequence that isexpected at the beginning of the signalling pattern (can be listed intables on receiver side). If the sequence is found within the receivedsymbol, the receiving apparatus 83 knows the exact frequency offset andcompensate it. More specifically, the obtained integer frequency offsetcan be supplied to and used in the reconstructing means 71 and thede-mapping means 72 for correctly demodulating the first signallingdata, as well as supplied to and used in the channel estimation means 69in order to perform the channel estimation and therefore theequalization.

The necessary time synchronization as well as the fractional frequencyoffset detection and compensation are for example done in the timedomain on the received time domain symbols in the time synchronizationmeans 66 and the fractional frequency offset detection means 67 usingguard interval correlation using the guard intervals of the receivedsignalling symbols and/or data symbols (cf. FIG. 13 showing a timedomain representation of a frame with signalling symbols, data symbols,and guard intervals). The time synchronization could alternatively bedone by performing a correlation of the absolute values between thereceived time domain symbols and a receiver generated time domainsymbol, in which only pilot signals are modulated. A peak in thecorrelation of the received symbol and the receiver generated symbolallows an exact time synchronization.

According to a second aspect which is schematically shown in FIG. 10,each signalling pattern 31 a (or signalling pattern 31) comprises atleast one pilot band 18, 19 comprising pilot signals mapped on thefrequency carriers 20, 21 of the pilot band 18, 19. The pilot bands 18,19 respectively comprise a number of immediately adjacent frequencycarriers on which pilot signals are mapped. The pilot bands 18, 19 mayeach have the same number of frequency carriers or a different number offrequency carriers. Hereby, each signalling pattern 31 a may comprise apilot band 18, 19 at its beginning or at its end (in the frequencydirection). Alternatively, each signalling pattern may comprise a pilotband 18, 19 at each border, i.e. at the beginning and at the end of thepattern. All other statements and definitions made above in relation tothe first aspect of the present invention also apply to the secondaspect, including Option 1 and Option 2. It has to be understood thatthe first and the second aspect could be combined, i.e. each signallingpattern may comprise at least one pilot band 18, 19 as described aboveas well as pilot signals mapped on every m-th frequency carrier 12.

In both aspects of the present invention described above, the relationbetween number of frequency carriers with pilot signals and the numberof frequency carriers with first signalling data in each signallingpattern might be variable and subject to the respective signalling andoffset compensation requirements.

As schematically shown in FIG. 11, the transmitting apparatus 82 mayblank (notch) certain regions 22, 23 of the overall transmissionbandwidth in order to avoid disturbances from the cable network intoother services, e.g. aircraft radio. Therefore, some part of thespectrum may not be modulated. In this case, the affected frequencycarriers within the signalling pattern 31; 31 a, 31 b shall not bemodulated as well. As the synchronization proposed by the presentinvention is very strong, this does not affect the frequencysynchronization performance by means of the D-BPSK modulated pilots. Themissing part of the first signalling data is recovered by means of therepetition of the first signalling data (every signalling pattern 31; 31a, 31 b in a frame comprises identical or almost identical firstsignalling data), e.g. by combining parts from two adjacent signallingpatterns as shown in FIG. 11, and eventually by means of the strongerror protection added to the signalling patterns by a error codingmeans 56 comprised in the transmitting apparatus 82. Missing parts offirst the signalling data at the edges of the transmission bandwidthshall be treated as very broad notches.

An alternative or additional possibility to deal with notches or otherproblems could be to subdivide the signalling pattern 31; 31 a, 31 binto two or more parts and to invert the sequence of the two or moreparts in each signalling pattern (of a frame) from frame to frame. Forexample, if the first signalling pattern in a frame is subdivided in afirst and a (succeeding) second part, the (corresponding) firstsignalling pattern in the immediately next frame would have the secondpart at the beginning and the first signalling part succeeding, i.e. aninverted sequence. Thus, if for example the second part is notched orotherwise disturbed, the receiver would have to wait for the next framewhere the second part could be received without problems (since thesucceeding first part would be disturbed).

An adaptation of the signalling patterns 31; 31 a, 31 b to differenttuning bandwidths of the receiving side may for example be done bychanging the distance of the frequency carriers in the signallingpatterns. Alternatively, it is possible to keep the frequency carrierdistance constant and to cut parts of the signalling patterns at theedges of the transmission bandwidth, e.g. by not modulating therespective frequency carriers, as schematically shown in FIG. 12, whichshows the adaptation of a scheme with 4 MHz signalling patterns to a 6MHz tuning bandwidth thus enabling the reception of data patterns havinga length up to 6 MHz.

Eventually, each signalling pattern 31; 31 a, 31 b could additionallycomprise a guard band at the beginning and the end of each pattern.Alternatively, in some applications it might be advantageous if only thefirst signalling pattern in each frame, in the example of FIG. 4 thesignalling pattern at position 39, could comprise a guard band only atthe beginning of the pattern, and the last signalling pattern in eachframe could comprise a guard band only at the end of the pattern.Alternatively, in some applications only the first signalling pattern ineach frame, in the example of FIG. 4 the signalling pattern at position39, could comprise a guard band at the beginning as well as at the endof the pattern, and the last signalling pattern in each frame couldcomprise a guard band at the beginning as well as at end of the pattern.The length of the guard band comprised in some or all of the signallingpatterns could for example be smaller or at maximum equal to the maximumfrequency offset the receiving apparatus can cope with. In the mentionedexample of a receiver bandwidth of 8 MHz, the guard band could forexample have a length of 250 to 500 kHz or any other suitable length.Also, the length of each of the guard bands comprised in the signallingpatterns could be at least the length of the carriers which are notreceived in the receiving apparatus due to the filter characteristics asdescribed in relation to FIG. 6.

For example, in an OFDM system in which the overall transmissionbandwidth is a multiple of 8 MHz (4nk mode: k is the Fourier window sizeof 1024 carriers/samples, n=1, 2, 3, 4 . . . ) and each signallingpattern has a length of 4 MHz, a suggestion for the length of each guardband at the beginning and the end of each signalling pattern would be343 frequency carriers (which is the number of not used carriers in thedata patterns at the beginning and end of each frame in each 4nk mode).The resulting number for usable carriers in each signalling patternwould be 3584/2−2×343=1106 carriers. It has to be understood, however,that these numbers are only used as examples and are not meant to belimiting in any sense. Hereby, the length of each of the guard bandscomprised in the signalling patterns could be at least the length of thecarriers which are not received in the receiving apparatus due to thefilter characteristics as described in relation to FIG. 6, so that thelength of the signalling data in each signalling pattern is equal to (ormay be smaller than) the effective receiver bandwidth. It should benoted that if additional signalling patterns 31 b are present, they willhave identical guard bands as the signalling patterns 31 a.

Additionally or alternatively, each data pattern could comprise a guardband with unused carriers at the beginning and the end of each pattern.Alternatively, in some applications only the respective first datapatterns in each frame in the frequency direction, in the example ofFIGS. 10 and 13 the data patterns 32, 32′, 32″, 32′″, 32″″ couldcomprise a guard band only at the beginning of the data pattern, and thelast data patterns in each frame in the frequency direction, in theexample of FIGS. 4 and 7 the data patterns 37, 37′, 37″, 37′″, 37″″could comprise a guard band at the end of the data pattern. Hereby, thelength of the guard bands of the data patterns could for example be thesame as the length of the guard bands of the signalling patterns if thesignalling patterns comprise guard bands.

As stated above the first signalling data comprised in the signallingpatterns 31, 31 a and or 31 b (or other signalling patterns according tothe present invention) comprise the physical layer information, whichenables a receiving apparatus 83 according to the present invention toobtain knowledge about the frame structure and to receive and decode thewanted data patterns. As a non limiting example, the first signallingdata could comprise parameters such as the overall or entiretransmission bandwidth, the location of the respective signallingpattern within the frame, the guard band length for the signallingpatterns, the guard band length for the data patterns, the number offrames which build a super frame, the number of the present frame withina super frame, the number of data patterns in the frequency dimension ofthe overall frame bandwidth, the number of additional data patterns inthe time dimension of a frame and/or individual signalling data for eachdata pattern in each frame. Hereby, the location of the respectivesignalling pattern within a frame can e.g. indicate the position of thesignalling pattern in relation to the segmentation of the overallbandwidth. For example, in the case of FIG. 4, the first signalling datacomprise indication if the signalling pattern is located in the firstsegment (e.g. the first 8 MHz segment), or the second segment etc. Incase of the signalling patterns having half the length of the bandwidthsegmentation, as e.g. explained in relation to FIG. 7, each pair ofadjacent signalling patterns then has the same location information. Inany case, the receiving apparatus will be able to tune to the wantedfrequency band in the succeeding frame using this location information.The individual (first) signalling data are a separate block of dataindividually provided for each data pattern present in the frame and maycomprise parameters such as the first frequency carrier of the datapattern, the number of frequency carriers allocated to the data pattern(or the length of a data pattern in terms of multiples of the minimumdata pattern length in the frequency direction), the usage of a timeinterleaver for the data pattern, the number of frequency notches(frequency carriers which are not used for data transmission in datapattern) in the data pattern, the position of the frequency notchesand/or the width of the frequency notches. The frame forming means 59 ofthe transmitting apparatus 82 is adapted to arrange the correspondingfirst signalling data in each signalling pattern. The evaluation means73 of the receiving apparatus 83 is adapted to evaluate the receivedsignalling data and to use or forward the information comprised in thefirst signalling data for further processing within the receivingapparatus 83.

In case that the first signalling data comprise the mentioned individualsignalling information for each data pattern present in a frame, thestructure of the signalling patterns support a maximum limited number ofdata patterns in the frequency direction per frame in order to restrictthe size of each signalling pattern to a maximum size. Thus, althoughthe number of data patterns in the frequency direction of each framecould be dynamically and flexible changed, this would then be true onlywithin a certain maximum number of data patterns. The additional datapatterns in the time direction of each frame are respectively alignedwith the preceding data patterns, as explained above. Thus, eachadditional succeeding data pattern has the same position, length,modulation etc. as the preceding data pattern so that the signallingdata for the preceding data pattern are also valid for the succeedingdata pattern. Hereby, the number of additional data patterns in the timedirection of each frame could be fixed or flexible and this informationcould also be comprised in the signalling data. Similarly, the structureof the signalling patterns could support only a maximum limited numberof frequency notches in each data pattern.

Alternatively or additionally, in order to overcome the problem thatparts of the signalling patterns 31 may not be receivable in thereceiving apparatus 83, the transmitting apparatus 82 could optionallycomprise an error coding means 56 arranged before the modulating means55 and adapted to add some kind of error coding, redundancy, such asrepetition coding, cyclic redundancy coding, or the like to the firstsignalling data. The additional error coding would enable thetransmitting apparatus 82 to use signalling patterns 31 in the samelength as the training patterns 30, as shown in FIG. 4 since thereceiving apparatus 83 is able, for example, by means of thereconstruction means 71, to perform some kind of error detection and/orcorrection in order to reconstruct the original signalling pattern.

For the mentioned example of the signalling patterns having a length of4 MHz and are aligned to segments of 8 MHz in an OFDM system, in thefollowing a specific (non-limiting) example of a signalling structure isdescribed.

For an OFDM symbol duration of 448 μs, each 4 MHz block is built by 1792OFDM subcarriers. If a frequency domain pilot is used on every 7^(th)OFDM carrier within the signalling symbols 1536 OFDM carriers remain forthe transmission of the L1 signalling data within each signalling OFDMsymbol.

These OFDM carriers may be e.g. modulated by 16QAM, resulting in gross6144 transmittable bits within the L1 signalling. Part of thetransmittable bits have to be used for error correcting purposes, e.g.for a LDPC or Reed Solomon code. The remaining net bits are then usedfor the signalling, e.g. as described in the table below.

GI Length Frame number Total bandwidth Total number of data slices L1sub-signalling table number Number of sub-tabled data slices Loop overdata slices {  Data slice number  Start subcarrier frequency  Number ofsubcarriers per slice  Time Interleaver depth  PSI/SI reprocessing Number of notches  Loop over notches {   Start of notch relative tostart of slice   Notch width  } End notch loop } End data slice loopReserved bits CRC_32

In the following, the parameters of the signalling data mentioned in theabove table are described in more detail:

GI Length:

-   -   Defines the length of used Guard Interval

Frame Number:

-   -   Counter which is increased every frame, i.e. each signalling        symbol

Total Bandwidth:

-   -   The complete transmission bandwidth of the used channel

Total Number of Data Slices:

-   -   This parameter signals the total number of data slices, i.e.        data patterns, in the used channel

L1 Sub-Signalling Table Number:

-   -   Number of the sub-signalling table within the signalling data

Number of Sub-Tabled Data Slices:

-   -   Number of data slices that are signalized within this L1        signalling table

Data Slice Number:

-   -   Number of the current data slice

Start Subcarrier Frequency:

-   -   Start frequency of the data slice

Number of Subcarriers Per Slice:

-   -   Number of subcarriers per data slice

Time Interleaver Depth:

-   -   Time interleaving depth within the current data slice

PSI/SI Reprocessing:

-   -   Signalizes, whether PSI/SI reprocessing has been performed in        the transmitter for the current data slice

Number of Notches:

-   -   Number of notches within the current data slice

Start of Notch Relative to Start of Slice:

-   -   Start position of the notch within the data slice with respect        to the start frequency of the data slice

Notch Width:

-   -   Width of the notch

Reserved Bits:

-   -   Reserved bits for future use

CRC_(—)32:

-   -   32 bit CRC coding for the L1 signalling block

In order to ensure an even better reception of the signalling patternsin the receiving apparatus 83, the present invention further suggests tooptimize the tuning position of the receiving apparatus 83. In theexamples shown in FIGS. 4 and 7, the receiver is tuned to a part 38 ofthe transmission bandwidth by centering the part 38 around the frequencybandwidth of the data patterns to be received. Alternatively, thereceiving apparatus 83 could be tuned so that the reception of thesignalling pattern 31 is optimized by placing the part 38 so that amaximum part of a signalling pattern 31 is received while the wanteddata pattern is still fully received. Alternatively, the length of therespective data patterns could not differ from the length of therespective signalling patterns 31 by more than a certain percentage forexample 10%. An example for this solution can be found in FIG. 8. Theborders between the data patterns 42, 43, 44 and 45 are (in thefrequency direction) not deviating from the borders between thesignalling patterns 31 by more than a certain percentage, such as (butnot limited to) 10%. This small percentage can then be corrected by theabove-mentioned additional error coding in the signalling patterns 31.

FIG. 13 shows a time domain representation of an example of frame 47according to the present invention. In the transmitting apparatus 82,after the frame pattern or structure was generated in the frame formingmeans 59, the frequency domain frame pattern is transformed into thetime domain by a frequency to time transforming means 60. An example ofa resulting time domain frame is now shown in FIG. 13 and comprises aguard interval 49, a signalling symbol 50, a further guard interval 51and a number of data symbols 52, which are respectively separated byguard intervals 53. While the situation that only a single signallingsymbol is present in the time domain corresponds to the example shown inFIG. 4, where only a single time slot with signalling patterns ispresent in the frequency domain frame structure, the example of FIG. 7with two time slots with signalling patterns 31 a and 31 b,respectively, would lead to the presence of two signalling patterns inthe time domain, which are eventually separated by a guard interval. Theguard intervals could e.g. be cyclic extensions of the useful parts ofthe respective symbols. In the example of an OFDM system, the signallingsymbols and the data symbols, including their eventually provided guardbands, could respectively have the length of one OFDM symbol. The timedomain frames are then forwarded to a transmitting means 61 whichprocesses the time domain signal depending on the used multi-carriersystem, for example by up-converting the signal to the wantedtransmission frequency. The transmission signals are then transmittedvia a transmitting interface 62, which can be a wired interface or awireless interface, such as an antenna or the like. As mentioned above,the signalling patterns(s) could be preceded by one or more trainingpatterns, which would lead to the presence of a training symbolpreceding the signalling symbol in the time domain.

FIG. 13 further shows that a respective number of frames could becombined to super frames. The number of frames per super frame, i.e. thelength of each super frame in the time direction, could be fixed orcould vary. Hereby, there might be a maximum length up to which thesuper frames could be set dynamically. Further, it might be advantageousif the signalling data in the signalling patterns for each frame in asuper frame are the same and if changes in the signalling data onlyoccur from super frame to super frame. In other words, the modulation,coding, number of data patterns etc. would be the same in each frame ofa super frame, but could then be different in the succeeding superframe. For example, the length of the super frames in broadcast systemscould be longer since the signalling data might not change as often, andin interactive systems the super frame length could be shorter since anoptimization of the transmission and reception parameters could be doneon the basis of feedback from the receiver to the transmitter. Asmentioned, a training symbol could precede each signalling symbol ineach frame.

The elements and functionalities of the transmitting apparatus 82, ablock diagram of which is shown in FIG. 14, have been explained before.It has to be understood, that an actual implementation of a transmittingapparatus 82 will contain additional elements and functionalitiesnecessary for the actual operation of the transmitting apparatus in therespective system. In FIG. 14, only the elements and means necessary forthe explanation and understanding of the present invention are shown.The same is true for the receiving apparatus 83, a block diagram ofwhich is shown in FIG. 15. FIG. 15 only shows elements andfunctionalities necessary for the understanding of the presentinvention. Additional elements will be necessary for an actual operationof the receiving apparatus 83. It has to be further understood that theelements and functionalities of the transmitting apparatus 82 as well asthe receiving apparatus 83 can be implemented in any kind of device,apparatus, system and so forth adapted to perform the functionalitiesdescribed and claimed by the present invention.

As mentioned above, the data in the data patterns of the presentinvention, such as the data patterns in the frames with the framestructures 29 and 29′ as shown in FIGS. 4 and 7, respectively, arearranged in data frames, wherein each data frame comprises secondsignalling data and content data. The second signalling data are herebysignalling data with individual parameters of the content data of therespective data frame, such as but not limited to the modulation usedfor the content data in the data frame, the error protection code usedfor the content data in the data frame, connection identification withinformation for the receiving apparatus if the content data comprise andthe data frame are intended for the receiving apparatus or not, and soforth.

As shown in FIG. 17, a data frame 84 of the present invention couldcomprise the second signalling data in a header 84 a, which is followedby the content data 84 b (in the time direction). That is, FIG. 17 showsa data frame 84 of the present invention which is formed by the dataframe forming means 54, 54′, 54″ of the transmitting apparatus 82 asshown in FIG. 14.

FIG. 18 schematically shows how several data frames are allocated to andinserted in data patterns which have the same frequency allocation andare adjacent in the time dimension, such as the data patterns 34, 34′,34″, 34′″ and 34″″ of the frames with the frame structures 29 and 29′shown in FIGS. 4 and 7, respectively. As shown in FIG. 18, several dataframes 85, 85′, 85″ and 85″″ of respectively different lengths (and/ordifferent data and/or signalling content and/or different modulationand/or different coding) are allocated to the data patterns 34, 34′,34″, 34′″ and 34″″ in a completely independent and flexible manner. Inother words, the length (number of frequency carriers) of the dataframes 85, 85′, 85″ and 85′″ is completely independent from the length(number of frequency carriers) of the data patterns 34, 34′, 34″, 34′″and 34″″ and the data frames 85, 85′, 85″ and 85′″ are arrangedsucceeding each other in the data patterns 34, 34′, 34″, 34′″ and 34″″.Thus the structure of the data frames generally is completelyindependent from the overall frame structure (e.g. frames with the framestructures 29 and 29′). However, the frequency structure, i.e. the firstfrequency carrier and the last frequency carrier of the data patterns34′, 34″, 34′″ and 34″″ is also the frequency structure of the dataframes 85, 85′, 85″ and 85′″. The data patterns having the samefrequency allocation and being adjacent to each other in the timedimension thus form a kind of a container for the data frames, which canbe inserted into the container completely freely and independently. Itis to be noted that FIG. 18 shows the data frame 85, 85′, 85″ and 85′″without being time and/or frequency interleaved for the sake of clarity.In an actual implementation, the data frame 85, 85′, 85″ and 85′″ wouldbe inserted into the data patterns 34, 34′, 34″, 34′″ and 34″″ in timeand/or frequency interleaved form.

The second signalling data contained in each header 85 a, 85 a′, 85 a″and 85 a′″ of each of the data frames 85, 85′, 85″, 85′″ containsindividual second signalling data for the respective data frame. Inother words, the second signalling data comprised in the header 85 a, 85a′, 85 a″ and 85 a′″ are at least partially different from each other.The length of each data frame 85, 85′, 85″ and 85′″ could be signalledeither in the second signalling data of a frame or in the firstsignalling data is described above. As mentioned above, the secondsignalling data could comprise the modulation of the content data in therespective data frame, the (error) coding of the content data in therespective data frame and/or connection identification. Additional oralternative signalling content could be also comprised in the secondsignalling data depending on the wanted implementation. For example, thesecond signalling data could (implicitly or explicitly) comprise someindication of the length of the content data in a data frame. In someimplementations, if the modulation and the coding is the same, thelength of the content data is also the same. Thus, in case in which themodulation and the coding of the content data in succeeding data framesstays the same, it might not be necessary to signal (in the header ofthe succeeding data frame) the same modulation and coding again but toonly indicate that the modulation and the coding stays the same asbefore. Alternatively, implementation might be possible where the headerof a succeeding data frame can be omitted if the modulation and thecoding do not change in relation to the preceding data frame.

The second signalling data of each data frame 85, 85′, 85″, 85′″advantageously comprise a synchronization sequence, such as apseudo-noise sequence or any other suitable sequence, which is used in acorrelation means 78 of the receiving apparatus 83 to perform acorrelation in order to detect the start of each header 85 a, 85 a′, 85a′″. Since the symbol synchronization has already taken place (wasachieved e.g. by a multi-carrier demodulation), the result of thecorrelation performed in the correlating means 78 allows the de-mappingmeans 70 to correctly de-map and demodulate the second signalling dataand the respective data frame. In an implementation example, the secondsignalling data are arranged in symbols and each of the symbolscomprises a part of the synchronization sequence (each symbol comprisesa number of bits). For example the most significant bit (or the mostsignificant bits, e.g. 2, 3 or 4 etc. bits) of each symbol comprises thepart of said synchronization sequence. For example, in case that thesecond signalling data are 16-QAM modulated, in which case the resulting16-QAM symbols respectively comprise 4 bits, the most significant bit ofeach of the QAM symbols comprised in each of the headers 85 a, 85 a′, 85a″, 85 a′″ could comprise a part (one bit) of the synchronizationsequence. Instead of the most significant bit(s), another bit or otherbits could be used. The synchronization sequence can be any kind ofsuitable sequence, e.g. a pn, a PRBS or any other sequence.

FIG. 19 shows an example of a part of the transmitting apparatus 82 inmore detail. Hereby, the second signalling data are encoded in anencoding means 86 and afterwards modulated, for example by QAM, QPSK orany other suitable method in a modulating means 87, where after themodulated and encoded second signalling data are supplied to a dataframe forming means 54 or 54′ or 54″. The content data are coded in acoding means 88, which is for example a LDPC (low density parity check)encoder or any other suitable encoder, afterwards interleaved by a bitinterleaver 89 and then modulated in a modulating means 58, 58′, 58″,which is for example a QAM or any other suitable encoder. The codedinterleaved and modulated content data are then supplied to a data frameforming means 54 (or 54′ or 54″). The data frame forming means 54, 54′,54″ then forms respective data frames as explained in relation to FIGS.17 and 18. Therefore, the block size of the coding performed by thecoding means 88 for the content data in each data frame can be variedfor each data frame, thus allowing a varying robustness level for thedata frames. The coding performed in the coding means 88 as well as themodulation performed in the modulating means 90 are respectivelysignalled in the second signalling data of the respective header of thedata frame. The modulation performed by the modulating means 87 on thesecond signalling data is e.g. a 16 QAM modulation (as described in moredetail in relation to FIG. 20) or a QPSK modulation (as described inmore detail in relation to FIG. 21), but any other robust modulation canbe used.

FIG. 20 shows a first example of a more detailed implementation of thegeneration of a header with second signalling data. In the shownexample, a 16 QAM modulation is performed by the modulating means 87 onthe second signalling data. Thus, a QAM symbol has 4 bits. The mostsignificant bit in each of the symbols is used for a part of thepseudo-noise sequence (pn sequence). The other three bits of each QAMsymbol carry the payload of the signalling data, such as the (error)coding of the content data, the modulation of the content data and/orthe connection identification. For example, the modulation informationis comprised in 3 bits, the connection identification is comprised in 8bits and the coding information is comprised in 4 bits, resulting a 15bit payload for a second signalling data. These 15 bits are repeated ina repeater 91, for example 3 times. Then, the second signalling data areencoded in an encoding means 86, which is for example a Reed Solomoncoding means and then supplied to the modulating means 87. Themodulating means 87 therefore outputs 45 symbols (the pseudo-noisesequence has a length of 45 bits, each of the bits being used as themost significant bit of each of the 45 symbols). It has to be noted,however, that the given numbers are only examples and can be changeddepending on the respective implementation.

FIG. 21 shows a second example of a more detailed implementation of thegeneration of a data frame header with second signalling data. Incontrary to the first example of FIG. 20, in which the synchronizationsequence is inserted in the second signalling data, this second examplesuggests to modulate the synchronization sequence onto the secondsignalling data. Further, the second example suggests to feed the secondsignalling data to an I and a Q path of the modulating means and toresort (i.e. to reorder) the data in the I or the Q path (for example bydelaying it or by shifting it), while modulating the synchronizationsequence onto one of the paths. Hereby, the diversity of the secondsignalling data is achieved which results in improved decodingproperties on the receiving side. In the second example, modulation,e.g. a QPSK modulation, is performed by the modulating means 87 on thesecond signalling data. A QPSK modulation is more robust than a 16 QAMmodulation as described in the example of FIG. 20. A QPSK symbolcomprises 2 bits, whereby each symbol carries a part of asynchronization sequence, which could for example be a pn sequence, aPRBS sequence or any other suitable sequence with good correlationproperties, as generally explained in relation to FIG. 19. In theimplementation example of FIG. 21, the encoding means 86 is for examplea BCH encoder (Block Code Encoder) which encodes the second signallingdata, which could for example be represented by 15 bits, 18 bits or thelike (for example the BCH encoder could be a BCH (18, 45) encoder). Theencoding means 86 then outputs e.g. 45 bits of encoded second signallingdata which are then fed to an I and a Q path of the modulating means 87.In the I path, the 45 encoded signalling bits are fed to the modulatingmeans 87 in unchanged form. However, in the Q path, the encodedsignalling bits are resorted by any suitable resorting process, e.g.delayed (e.g. delayed by a one bit cyclic shift), shifted, reordered orthe like, in a resorting means 90, where after the synchronizationsequence (for example a pn sequence, a PRBS sequence any other suitablesynchronization sequence with good correlation properties) is modulatedonto the resorted bits by means of a combining means 92, which performsfor example a XOR operation or any other suitable operation. Thesynchronization sequence for example also comprises 45 bits, so that incases the resorting means 90 introduces a one bit cyclic shift, eachshifted bit of the Q path is modulated with one bit of thesynchronization sequence. The resorted bits with the modulatedsynchronization sequence are then supplied on the Q path to themodulating means 87, which performs e.g. a QPSK modulation on thesignals supplied via the I and Q path. The modulating means 87 thenoutputs modulated second signalling information in form of symbols, inthe present example 45 symbols in each header of each data frame. Eachsymbol comprises a number of bits (in the QPSK example two bits),wherein, in the present example one of the bits is modulated with onebit from the synchronization sequence. Generally, a part of thesynchronization sequence is modulated onto one or more of the bits ofeach symbol. It has to be understood that instead of the Q path, the Ipath could be delayed and modulated with the synchronization sequence.As shown in FIG. 19, the modulated second signalling data are thensupplied from the modulating means 87 to the data frame forming means 54(or 54′ or 54″) as shown and described in relation to FIG. 19.

FIG. 22 shows an implementation detail of the receiving apparatus 83 asshown in FIG. 15 for the implementation example of FIG. 21. FIG. 22hereby shows an implementation example for the synchronization detectionof the data frames by means of the synchronization sequence comprised ineach data frame header. As shown in FIG. 22, the data output from thetime de-interleaver 77 are supplied to a demodulating means 93, forexample a hard decision demodulating means, such as, in the context ofthe example of FIG. 21, e.g. a QPSK de-mapping means, which e.g. QPSKdemodulates the second signalling data and outputs the demodulated datain a I and Q path. A resorting means 94 in the I path resorts, e.g.delays, shifts or the like, the data in order to at least partiallycompensate the resorting introduced to the data in the Q path by theresorting means 90 as shown in FIG. 21. It has to be noted that theoperation performed by the resorting means 94 can but does not need tobe fully reversible to the operation performed by the sorting means 90.Also, if the resorting means 90 is located in the I path, the resortingmeans 94 is located in the Q path. Then, the data on the I path aremultiplied with the data on the Q path in a multiplication means 95,which results in the synchronization sequence, which was modulated ontothe data frame header, and which is output to the correlating means 78,which performs a correlation with the known (expected) synchronizationsequence and outputs a synchronization peak enabling the detection of adata frame header and thus of a data frame beginning. The resultinginformation is then for example supplied to the de-mapping means 70 asshown and described in relation to FIG. 15.

FIG. 23 shows an implementation detail of the receiving apparatus 83 asshown in FIG. 15 in relation to the examples of FIGS. 21 and 22. Hereby,FIG. 23 comprises a suggestion for an implementation in order to obtainand evaluate the second signalling data contained in the data frameheaders (as for example generally described in relation to theevaluation means 79 of the receiving apparatus 83 shown in FIG. 15).Hereby, in the example of FIG. 23, the data stream coming from the timede-interleaver 77 of the receiving apparatus 83 of FIG. 15 is suppliedto a de-mapping means 96, which is for example a soft decision QPSKde-mapping means. The de-mapping means 96 QPSK demodulates the data andoutputs them in an I and a Q path. Advantageously, the data are outputin a log likelihood ratio form. In the Q path, the data are modulated ina combining means 97 with an expected copy (or suitably processed copy)of the synchronization sequence comprised in the data frame headers(modulated onto the second signalling data in the transmitting apparatus82), where after the data are resorted (e.g. delayed, shifted or thelike) in a resorting means 98 in order to reverse the resortingintroduced by the resorting means 90 to the data in the Q path as shownin FIG. 21. It has to be noted that the resorting performed by theresorting means 98 should be fully reversible to the resortingintroduced by the resorting means 90. Also, the resorting means 98 aswell as the combining means 97 should be located in the I path in casethat the resorting means 90 and the combining means 92 are located inthe I path. Afterwards, the data of the I and the Q path are summed inan adding means 99, where after a hard decision is applied to the addeddata in a hard decision means 100. The output of the hard decision meansis then decoded in a decoding means 101, for example a block codedecoding means which decodes the coding introduced by the encoding means86 of FIG. 21. The output of the decoding means 101 are then theoriginal second signalling data, as for example the bits or 18 bitssecond signalling data as supplied to the encoding means 86 of FIG. 21.These second signalling data are then used for the further processing,for example supplied to the de-mapping means 70 and/or the errordecoding means 80 of the receiving apparatus 83 of FIG. 15. It should benoted that the delaying means 98 could alternatively be implemented inthe I path. Also, additionally or alternatively, the I and the Q pathcould be decoded separately and the path with the better decoding resultcould be further used.

The ordering of the second signalling data and the content data in dataframes and to allocate the data frames to the data patterns in anindependent and flexible manner has the advantage that a reducedprocessing in the receiving apparatus 83 is necessary. Further, onlyshort delays for interactive services are guaranteed. As shown in FIG.15, the receiving apparatus 83, after the correlating means 78 providingthe correlation of the synchronization (pseudo-noise) sequence of thesecond signalling data, comprises an evaluation means 79 which isadapted to evaluate the received second signalling data, eventuallyafter a necessary decoding corresponding to the coding performed by theencoding means 86, a demodulation (e.g. QAM demodulation) correspondingto the modulation performed by the modulating means 87 or othernecessary processing. However, the signalling information obtained bythe evaluation means 79 is supplied to the de-mapping means 70. Forexample, the evaluation means 79 can be adapted to obtain the modulationof the content data from the second signalling data and provide thede-mapping means 70 with the modulation information so that thede-mapping means 70 can perform the respectively necessary demodulationon the content data of the data frame. Further, the evaluation means 79may be adapted to obtain the error coding of the content data in a dataframe and to provide an error decoding means 80 located in the receivingapparatus 83 so that the error decoding means 80 is adapted to performan error decoding on the content data of a received data frame. Further,the evaluation means 79 may be adapted to obtain connection informationin the second signalling data of a received data frame and to provide asuitable processing means of the receiving apparatus 83 with theconnection information informing the receiving apparatus 83 if thecontent data of a received data frame are actually intended to bereceived by the receiving apparatus 83 or not.

It is to be noted that the present invention is intended to cover aframe structure (and a correspondingly adapted transmitting andreceiving apparatus and method as described above), which, as analternative to the above described embodiments, does have a number (twoor more) data patterns in which at least one data pattern has a lengthwhich is different from the length of the other data pattern(s). Thisstructure of data patterns with a variable length can be combined eitherwith a sequence of signalling patterns with identical lengths and(identical or almost identical) contents as described above, or with asequence of signalling patterns in which at least one signalling patternhas a length and/or a content different from the other signallingpatterns, i.e. a variable signalling pattern length. In both cases, thereceiving apparatus 83 will need some information about the varying datapattern length, which could be transmitted by means of a separatesignalling data channel or by means of signalling data comprised insignalling data patterns comprised in the frame structure as describedabove. In the later case, it might be a possible implementation if thefirst signalling patterns in each frame always have the same length sothat the receiving apparatus can always obtain the information about thevarying data patterns by receiving the first signalling patterns inevery or the necessary frames. Of course, other implementations might bepossible. Otherwise, the rest of the above description in relation tothe data patterns and the signalling patterns as well as the possibleimplementations in the transmitting apparatus 82 and the receivingapparatus 83 is still applicable.

1. Transmitting apparatus (82) for transmitting signals in a multicarrier system on the basis of a frame structure, each frame comprisingat least one signalling pattern and one or more data patterns, saidtransmitting apparatus comprising frame forming means (59) adapted toarrange first signalling data in said at least one signalling pattern ina frame, and adapted to arrange data in said one or more data patternsin a frame, whereby the data of said one or more data patterns arearranged in data frames, each data frame comprising second signallingdata and content data, transforming means (60) adapted to transform saidat least one signalling pattern and said one or more data patterns fromthe frequency domain into the time domain in order to generate a timedomain transmission signal, and transmitting means (61) adapted totransmit said time domain transmission signal.
 2. Transmitting apparatus(82) according to claim 1, wherein the second signalling data in eachdata frame are arranged in a header of the data frame.
 3. Transmittingapparatus (82) according to claim 1, wherein the second signalling datacomprise a synchronization sequence.
 4. Transmitting apparatus (82)according to claim 3, wherein the second signalling data are arranged insymbols and a part of said synchronization sequence is inserted in eachsymbol.
 5. Transmitting apparatus (82) according to claim 3, wherein thesecond signalling data are arranged in symbols and a part of saidsynchronization sequence is modulated onto at least a part of eachsymbol.
 6. Transmitting apparatus (82) according to claim 1, wherein atleast one of said data patterns in a frame is followed by at least oneadditional data pattern in the time dimension with the same frequencystructure as said at least one of said data patterns, wherein dataframes arranged in said at least one of said data patterns and the atleast one additional data pattern are arranged succeeding each otherindependent of said frequency structure.
 7. Transmitting method fortransmitting signals in a multi carrier system on the basis of a framestructure, each frame comprising at least one signalling pattern and oneor more data patterns, comprising the steps of arranging signalling datain said at least one signalling pattern in a frame, arranging data insaid one or more data patterns in a frame, whereby the data of said oneor more data patterns are arranged in data frames, each data framecomprising second signalling data and content data, transforming said atleast one signalling pattern and said one or more data patterns from thefrequency domain into the time domain in order to generate a time domaintransmission signal, and transmitting said time domain transmissionsignal.
 8. Frame pattern for a multi carrier system, comprising at leastone signalling pattern and one or more data patterns, wherein data arearranged in said one or more data patterns in a frame, whereby the dataof said one or more data patterns are arranged in data frames, each dataframe comprising second signalling data and content data.
 9. Receivingapparatus (63) for receiving signals in a multi carrier system on thebasis of a frame structure in a transmission bandwidth, each framecomprising at least one signalling pattern comprising first signallingdata and one or more data patterns, whereby the data of said one or moredata patterns are arranged in data frames, each data frame comprisingsecond signalling data and content data, said receiving apparatus (63)comprising receiving means (65) adapted to be tuned to and to receive aselected part of said transmission bandwidth, said selected part of saidtransmission bandwidth covering at least one data pattern to bereceived, evaluation means (79) adapted to evaluate said secondsignalling data comprised in a received data frame, and data de-mappingmeans (70) adapted to de-map data from frequency carriers of a receiveddata frame on the basis of the result of said evaluation.
 10. Receivingapparatus (63) according to claim 9, wherein said second signalling datacomprise the modulation of said data in said received data frame,wherein said evaluation means (79) is adapted to obtain the modulationand said data de-mapping means (70) is adapted to perform a demodulationof data from frequency carriers of said received data frame on the basisof the obtained modulation.
 11. Receiving apparatus (63) according toclaim 9, wherein said second signalling data comprise the error codingof said data in said received data frame, wherein said evaluation means(79) is adapted to obtain the error coding and forward the error codingto a error decoding means (80) adapted to perform an error decoding ondata of said received data frame.
 12. Receiving apparatus (63) accordingto claim 9, wherein said second signalling data comprise connectionidentification and said evaluation means (70) is adapted to obtain saidconnection identification.
 13. Receiving apparatus (63) according toclaim 9, comprising a correlation means (78) adapted to perform acorrelation on a synchronization sequence comprised in said secondsignalling data of a received data frame, wherein said data de-mappingmeans (70) is adapted to de-map said data from frequency carriers ofsaid received data frame on the basis of the result of said correlation.14. Receiving method for receiving signals in a multi carrier system onthe basis of a frame structure in a transmission bandwidth, each framecomprising at least one signalling pattern comprising first signallingdata and one or more data patterns, whereby the data of said one or moredata patterns are arranged in data frames, each data frame comprisingsecond signalling data and content data, comprising the steps ofreceiving a selected part of said transmission bandwidth, said selectedpart of said transmission bandwidth covering at least one data patternto be received, evaluating said second signalling data comprised in areceived data frame, and de-mapping data from frequency carriers of areceived data frame on the basis of the result of said evaluation. 15.System for transmitting and receiving signals, comprising a transmittingapparatus (82) for transmitting signals in a multi carrier system on thebasis of a frame structure, each frame comprising at least onesignalling pattern and one or more data patterns, said transmittingapparatus comprising frame forming means (59) adapted to arrange firstsignalling data in said at least one signalling pattern in a frame, andadapted to arrange data in said one or more data patterns in a frame,whereby the data of said one or more data patterns are arranged in dataframes, each data frame comprising second signalling data and contentdata, transforming means (60) adapted to transform said at least onesignalling pattern and said one or more data patterns from the frequencydomain into the time domain in order to generate a time domaintransmission signal, and transmitting means (61) adapted to transmitsaid time domain transmission signal, said system further comprising areceiving apparatus (83) according to claim 10 adapted to receive saidtime domain transmission signal from said transmitting apparatus (82).16. Method for transmitting and receiving signals, comprising atransmitting method for transmitting signals in a multi carrier systemon the basis of a frame structure, each frame comprising at least onesignalling pattern and one or more data patterns, comprising the stepsof arranging signalling data in said at least one signalling pattern ina frame, arranging data in said one or more data patterns in a frame,whereby the data of said one or more data patterns are arranged in dataframes, each data frame comprising second signalling data and contentdata, transforming said at least one signalling pattern and said one ormore data patterns from the frequency domain into the time domain inorder to generate a time domain transmission signal, and transmittingsaid time domain transmission signal, said method further comprising areceiving method according to claim 14 adapted to receive said timedomain transmission signal.